Porous carbon materials for co2 separation in natural gas

ABSTRACT

In some embodiments, the present disclosure pertains to materials for use in CO 2  capture in high pressure environments. In some embodiments, the materials include a porous carbon material containing a plurality of pores for use in a high pressure environment. Additional embodiments pertain to methods of utilizing the materials of the present disclosure to capture CO 2  from various environments. In some embodiments, the materials of the present disclosure selectively capture CO 2  over hydrocarbon species in the environment.

RELATED APPLICATIONS

This application claims priority to and benefit of U.S. ProvisionalPatent Application No. 62/079,437, filed on Nov. 13, 2014; is acontinuation-in-part of U.S. patent application Ser. No. 14/458,802filed on Aug. 13, 2014, which claims priority to and benefit of U.S.Provisional Patent Application No. 61/865,323, filed on Aug. 13, 2013and U.S. Provisional Patent Application No. 62/001,552, filed on May 21,2014; is a continuation-in-part of U.S. patent application Ser. No.14/315,920, filed on Jun. 26, 2014, which claims priority to and thebenefit of U.S. Provisional Patent Application No. 61/839,567, filed onJun. 26, 2013; and is a continuation-in-part of U.S. patent applicationSer. No. 14/371,791, filed on Jul. 11, 2014, which is a U.S. nationalstage application of PCT/US2013/021239, filed on Jan. 11, 2013, andwhich claims priority to and benefit of U.S. Provisional PatentApplication No. 61/585,510, filed on Jan. 11, 2012. The entirety of eachof the aforementioned applications is incorporated herein by reference.

BACKGROUND

Current methods and materials for capturing CO₂ and H₂S from anenvironment suffer from numerous limitations, including low selectivity,limited sorption capacity, high sorbent costs, and stringent reactionconditions. The present disclosure addresses these limitations.

SUMMARY

In some embodiments, the present disclosure pertains to methods ofcapturing a gas from an environment. In some embodiments, the methodsinclude a step of associating the environment with a porous carbonmaterial. In some embodiments, the associating results in sorption ofgas components to the porous carbon material. In some embodiments, thesorbed gas components include at least one of CO₂, H₂S, and combinationsthereof.

In some embodiments, the environment in which gas capture occurs is apressurized environment. In some embodiments, the environment includes,without limitation, industrial gas streams, natural gas streams, naturalgas wells, industrial gas wells, oil and gas fields, and combinationsthereof.

In some embodiments, the sorbed gas components include CO₂. In someembodiments, the sorption of the CO₂ to the porous carbon materialoccurs selectively over hydrocarbons in the environment. In someembodiments, the CO₂ is converted to poly (CO₂) or a matrix of CO₂(e.g., a matrix of ordered CO₂) within the pores of the porous carbonmaterials. In some embodiments, the porous carbon material has a CO₂sorption capacity of about 50 wt % to about 200 wt % of the porouscarbon material weight when measured in absolute uptake values.

In some embodiments, the sorbed gas components include H₂S. In someembodiments, the H₂S is converted within the pores of the porous carbonmaterials to at least one of elemental sulfur (S), sulfur dioxide (SO₂),sulfuric acid (H₂SO₄), and combinations thereof. In some embodiments,the formed elemental sulfur becomes impregnated with the porous carbonmaterial. In some embodiments, captured H₂S remains intact within theporous carbon material. In some embodiments, the porous carbon materialhas a H₂S sorption capacity of about 50 wt % to about 300 wt % of theporous carbon material weight.

In some embodiments, the sorbed gas components include CO₂ and H₂S. Insome embodiments, the sorption of H₂S and CO₂ to the porous carbonmaterial occurs at the same time. In some embodiments, the sorption ofCO₂ to the porous carbon material occurs before the sorption of H₂S tothe porous carbon material. In some embodiments, the sorption of H₂S tothe porous carbon material occurs before the sorption of CO₂ to theporous carbon material.

In some embodiments, the methods of the present disclosure also includea step of releasing captured gas components from the porous carbonmaterial. In some embodiments, the releasing occurs by decreasing thepressure of the environment or heating the environment. In someembodiments, the releasing of sorbed CO₂ occurs by decreasing thepressure of the environment or placing the porous carbon material in asecond environment that has a lower pressure than the environment whereCO₂ capture occurred. In some embodiments, the releasing of sorbed H₂Soccurs by heating the porous carbon material. In some embodiments, thereleasing of the CO₂ occurs before the releasing of the H₂S.

In some embodiments, the methods of the present disclosure also includea step of disposing the released gas. In some embodiments, the methodsof the present disclosure also include a step of reusing the porouscarbon material after the releasing to capture additional gas componentsfrom an environment.

In some embodiments, the porous carbon material utilized for gas captureincludes a plurality of pores. In some embodiments, the porous carbonmaterial includes, without limitation, protein-derived porous carbonmaterials, carbohydrate-derived porous carbon materials, cotton-derivedporous carbon materials, fat-derived porous carbon materials,waste-derived porous carbon materials, asphalt-derived porous carbonmaterials, coal-derived porous carbon materials, coke-derived porouscarbon materials, asphaltene-derived porous carbon materials, oilproduct-derived porous carbon materials, bitumen-derived porous carbonmaterials, tar-derived porous carbon materials, pitch-derived porouscarbon materials, anthracite-derived porous carbon materials,melamine-derived porous carbon materials, biochar-derived porous carbon,wood-derived porous carbon and combinations thereof.

In some embodiments, the porous carbon material includes asphalt-derivedporous carbon materials. In some embodiments, the porous carbon materialis carbonized. In some embodiments, the porous carbon material isreduced. In some embodiments, the porous carbon material is vulcanized.In some embodiments, the porous carbon material includes a plurality ofnucleophilic moieties. In some embodiments, the nucleophilic moietiesinclude, without limitation, oxygen-containing moieties,sulfur-containing moieties, metal-containing moieties, metaloxide-containing moieties, metal sulfide-containing moieties,nitrogen-containing moieties, phosphorous-containing moieties, andcombinations thereof.

In some embodiments, the porous carbon materials may be derived from atleast one of biochars, hydrochars, charcoals, coal, activated carbon,and combinations thereof. These sources may be favorable when othersources (such as asphalt) are prohibitively expensive for a particularapplication. The cost of synthetic polymers may be seen as high comparedwith industrial waste or agriculture waste. Furthermore, in order toreach higher CO₂ uptake capacity, A-PC has to be N-doped by NH₃ followedby H₂ reduction at 700° C., which may not be favored by all industries.In some embodiments, the porous carbon materials of the presentdisclosure are biochar-derived porous carbon materials (B-PC). In someembodiments, the porous carbon materials of the present disclosure arebiochar-derived and nitrogen-containing porous carbon materials (B-NPC).In some embodiments, the biochar source is a carbon-rich materialproduced by pyrolysis of waste organic feedstock that has been used as asustainable means to sequester atmospheric carbon, improve soilfertility, waste management and to reduce CO₂ emissions. In someembodiments, the porous carbon materials of the present disclosure havea 1.50 g of CO₂ uptake capacity per gram of sorbent, which is ˜5 timeshigher than that in Zeolite 5A and 3 times higher than that in ZIF-8measured under the pressure of 30 bar at 23° C. In some embodiments, theporous carbon materials of the present disclosure (e.g., B-PC and B-NPC)can be spontaneously regenerated when the pressure returns to ambientpressure with the same CO₂ uptake performance—a pressure swing captureprocess. In some embodiments, the porous carbon materials of the presentdisclosure (e.g., B-PC and B-NPC) can also be used as metal-freecatalysts as well as sorbents for low-temperature oxidation of H₂S toelemental sulfur. In some embodiments, the biochars of the presentdisclosure (e.g., sulfur-rich B-PC and sulfur-rich B-NPC) can bepotentially used as cathode materials in lithium-sulfur batteries.

In some embodiments, the porous carbon materials have surface areasranging from about 2,500 m²/g to about 4,500 m²/g. Surface areas greaterthan about 3,000 m²/g may imply that the sorbent stacks into multilayerswithin the pore structures and along the surfaces. In some embodiments,the plurality of pores in the porous carbon material comprises diametersranging from about 1 nm to about 10 nm, and volumes ranging from about 1cm³/g to about 3 cm³/g. In some embodiments, the porous carbon materialhas a density ranging from about 0.3 g/cm³ to about 4 g/cm³.

Additional embodiments of the present disclosure pertain to the porouscarbon materials used for gas capture or gas separation or combinationsthereof. Further embodiments of the present disclosure pertain tomethods of making the porous carbon materials of the present disclosure.

DESCRIPTION OF THE FIGURES

FIG. 1 shows a scheme of a method of utilizing porous carbon materialsto capture gas (e.g., carbon dioxide (CO₂) or hydrogen sulfide (H₂S))from an environment (FIG. 1).

FIG. 2 shows schemes of CO₂ capture from materials relating to theformation of chemisorbed oxygen species on porous carbon materials as aresult of their reaction with H₂S and O₂. The porous carbon material wasfirst reacted with H₂S and air, and then thermalized with or withoutammonia, and finally used for reversible CO₂ capture.

FIG. 3 shows synthetic schemes and micrographic images of various porouscarbon materials. FIG. 3A provides a scheme for the synthesis ofsulfur-containing porous carbon (SPC) or nitrogen containing porouscarbon (NPC) by treating poly[(2-hydroxymethyl)thiophene] orpoly(acrylonitrile) with KOH at 600° C. and then washing with dilute HCland water until the extracts are neutral. The NPC is further reducedusing 10% H₂ at 600° C. to form reduced NPC (R-NPC). The syntheticdetails are described in Example 1. FIG. 3B shows a scanning electronmicroscopy (SEM) image of NPCs at a scale bar of 100 μm. FIG. 3C showsan SEM image of SPCs at a scale bar of 500 nm. FIG. 3D shows atransmission electron microscopy (TEM) image of the SPCs in FIG. 3B at ascale bar of 25 nm.

FIG. 4 shows x-ray photoelectron spectroscopy (XPS) of SPCs (left panel)and NPCs (right panel). The XPS indicates 13.3 atomic % of S in the SPCprecursor and 22.4 atomic % of N in the NPC precursor. The resulting SPCand NPC then had 8.1 atomic % of S content and 6.2 atomic % of Ncontent, respectively. The S2p and N1, XPS peaks were taken from the SPCand NPC. The S2p core splits into two main peaks of 163.7 (2p312) and164.8 eV (2p112), which correspond to thiophenic sulfur atomsincorporated into the porous carbon framework via the formation of C—S—Cbond. The N1 reflects two different chemical environments: pyridinicnitrogen (N-6) and pyrrolic nitrogen (N-5) atoms.

FIG. 5 shows data relating to CO₂ uptake measurements for SPCs. FIG. 5Ashows volumetric and gravimetric uptake of CO₂ on SPC at differenttemperatures and pressures. Data designated with (*) were recordedvolumetrically. Data designated with (§) were performed volumetrically.Data designated with (+) were measured gravimetrically at NIST. Allgravimetric measurements were corrected for buoyancy. FIGS. 5B-D showthree consecutive CO₂ sorption-desorption cycles on the SPC over apressure range from 0 to 30 bar at 30° C. All solid circles indicate CO₂sorption, while the open circles designate the desorption process. FIG.5E show volumetric SPC CO₂ sorption isotherms at 23° C. and 50° C. overa pressure range from 0 to 1 bar.

FIG. 6 shows pictorial descriptions of excess and absolute CO₂ uptake.FIG. 6A is adapted from Chem. Sci. 5, 32-51 (2014). The dashed lineindicates the Gibbs dividing surface. It divides the free volume intotwo regions in which gas molecules are either in an adsorbed or bulkstate. FIG. 6B shows a depiction of total uptake, which can be used asan approximation for absolute uptake for microporous materials withnegligible external surface areas.

FIG. 7 shows CO₂ uptake on the SPC. Comparison of absolute uptake andexcess uptake at 22° C. and 50° C. exemplifies the small differencesover this pressure and temperature range.

FIG. 8 shows spectral changes before and after sorption-desorption at23° C. and the proposed polymerization mechanism. Attenuated totalreflectance infrared spectroscopy (ATR-IR) (FIGS. 8A-B), Ramanspectroscopy (FIG. 8C) and 50.3 MHz ¹³C MAS NMR spectra (FIG. 8D) areshown before and after CO₂ sorption at 10 bar and room temperature. Allspectra were recorded at the elapsed times indicated on the graphs afterthe SPC sorbent was returned to ambient pressure. In the NMRexperiments, the rotor containing the SPC was tightly capped during theanalyses. For the third NMR experiment (top), the same material was leftunder ambient conditions for 19 h before being repacked in the rotor toobtain the final spectrum. Each NMR spectrum took 80 min to record.Example 1 shows more details. FIGS. 8E-F show proposed mechanisms thatillustrate the poly (CO₂) formation in SPC or NPC, respectively, in ahigher pressure CO₂ environment. With the assistance of the nucleophile,such as S or N, the CO₂ polymerization reaction is initiated underpressure, and the polymer is further likely stabilized by the van derWaals interactions with the carbon surfaces in the pores.

FIG. 9 shows ATR-IR (FIG. 9A) and Raman (FIG. 9B) spectra for the ZIF-8before and after CO₂ sorption at 10 bar. All spectra were recorded 3 and20 minutes after the ZIF-8 sorbent was returned to ambient pressure atroom temperature.

FIG. 10 shows ATR-IR (FIG. 10A) and Raman (FIG. 10B) spectra for theactivated carbon before and after CO₂ sorption at 10 bar. Spectra weretaken 3 min and 20 min after the activated carbon was returned toambient pressure at room temperature.

FIG. 11 shows volumetric gas uptake data. FIG. 11A shows data relatingto volumetric CO₂ uptake performance at 30° C. of SPC, NPC, R-NPC andthe following traditional sorbents: activated carbon, ZIF-8, and zeolite5A. Aluminum foil was used as a reference to ensure no CO₂ condensationwas occurring in the system at this temperature and pressure. VolumetricCO₂ and CH₄ uptake tests at 23° C. on SPC (FIG. 11B), activated carbon(FIG. 11C) and ZIF-8 sorbents (FIG. 11D) are also shown.

FIG. 12 shows various mass spectrometry (MS) data. FIG. 12A shows MSdata that was taken while the system was being pressurized with apremixed gas of CO₂ in natural gas during the uptake process. FIG. 12Bshows MS data that was recorded while the premixed gas-filled SPC wasdesorbing from 30 bar. The mixed gas was purchased from Applied Gas Inc.

FIG. 13 shows comparative data relating to the CO₂ uptake capacities ofvarious carbon sources.

FIG. 14 shows scanning electron microscopy (SEM) (FIG. 14A) andtransmission electron microscopy (TEM) (FIG. 14B) images of A-PCs.

FIG. 15 shows nitrogen sorption isotherms for A-PC, A-NPC and A-rNPC.

FIG. 16 shows schematic illustrations of the preparation ofasphalt-derived porous carbon materials (A-PCs). FIG. 16A shows a schemeof a method of preparing nitrogen-doped A-PCs (A-NPCs) and reducedA-NPCs (A-rNPC). FIG. 16B shows more detailed schemes of methods ofpreparing A-rNPCs, sulfur-doped APCs (A-SPC), and nitrogen-doped andsulfur doped APCs (A-NSPCs).

FIG. 17 shows a comparison of room temperature volumetric CO₂ uptake ofA-PC, A-NPC and A-rNPC with the other porous carbon sorbents and thestarting asphalt.

FIG. 18 shows data relating to the volumetric uptake of CO₂ on A-rNPC asa function of temperature at pressures that range from about 0-30 bar(FIG. 18A) and about 0-1 bar (FIG. 18B).

FIG. 19 shows data relating to the volumetric CO₂ and CH₄ uptake ofA-rNPC (squares) and A-SPC (circles) at 23° C.

FIG. 20 shows the gravimetric measurement of CO₂ and CH₄ uptake ofuGil-600, 700, 800, and 900 at 25° C. The uGil-T sorbents exhibit highCO₂ capacity (up to 1.50 g CO₂/g adsorbent at 54 bar) under highpressure environment, which is 9 times higher than Zeolite 5A, and 4times higher than ZIF-8 at the same conditions.

FIG. 21 shows the results of TEM EDS elemental mapping of A-rNPCs afterH₂S uptake under air treatment. FIG. 21A shows a TEM image of A-rNPCafter H₂S uptake. FIG. 21B shows carbon element mapping of A-rNPCs afterH₂S uptake. FIG. 21C shows sulfur elemental mapping of A-rNPCs after H₂Suptake.

FIG. 22 shows a thermogravimetric analysis (TGA) curve of A-rNPCs afterH₂S uptake with exposure to air.

FIG. 23 shows a summary of the H₂S uptake capacity of A-rNPC underdifferent conditions, and its comparison to the H₂S uptake capacity ofMaxsorb®, a commercial high surface area carbonized material.

FIG. 24 shows comparative data relating to the CO₂ uptake capacities ofA-rNPCs and A-NPCs.

FIG. 25 shows comparative data relating to the CO₂ uptake capacities ofA-NSPCs and A-SPCs.

FIG. 26 shows an SEM image of B-NPC (FIG. 26A), a TEM image of B-NPC(FIG. 26B), a BET isotherm curve of B-NPC, indicating B-NPC is amicroporous material with a surface area of 2988 m²/g (FIG. 26C), and aDFT size distribution of B-NPC, showing that the pore size is from 0.5-5nm (FIG. 26D).

FIG. 27 shows CO₂ uptake performances of different sorbents, B-NPC andC-NPC (charcoal derived N-containing porous carbon) at 25° C.

FIG. 28 shows CO₂ uptake performances of different B-PC prepared bydifferent bases.

FIG. 29 shows CO₂ uptake performances of different B-NPC prepared fromdifferent precursors using KOH as base.

FIG. 30 shows the thermogravimetric analysis (TGA) curves of B-NPC andC-NPC after H₂S capture.

FIG. 31 shows TGA curves of asphalts from different sources and theremoval of volatile oils between 400° C. and 500° C.

DETAILED DESCRIPTION

It is to be understood that both the foregoing general description andthe following detailed description are illustrative and explanatory, andare not restrictive of the subject matter, as claimed. In thisapplication, the use of the singular includes the plural, the word “a”or “an” means “at least one”, and the use of “or” means “and/or”, unlessspecifically stated otherwise. Furthermore, the use of the term“including”, as well as other forms, such as “includes” and “included”,is not limiting. Also, terms such as “element” or “component”respectively encompass both elements or components comprising one unitand elements or components that comprise more than one unit unlessspecifically stated otherwise.

The section headings used herein are for organizational purposes and arenot to be construed as limiting the subject matter described. Alldocuments, or portions of documents, cited in this application,including, but not limited to, patents, patent applications, articles,books, and treatises, are hereby expressly incorporated herein byreference in their entirety for any purpose. In the event that one ormore of the incorporated literature and similar materials defines a termin a manner that contradicts the definition of that term in thisapplication, this application controls.

Environmental and health concerns have been linked to carbon dioxide(CO₂) and hydrogen sulfide (H₂S) emission sources, such as industrialpower plants, refineries and natural gas wells. Therefore, efficient CO₂and H₂S capture from flue gases or other high pressure natural gas wellshas been a primary approach in mitigating environmental and healthrisks. For instance, aqueous amine solvents and membrane technologieshave been utilized for CO₂ capture. In addition, solid sorbents such asactivated carbon, zeolites and metal organic frameworks have beenutilized as alternative materials for capturing CO₂.

However, many of the aforementioned technologies suffer from numerouslimitations. For instance, many CO₂ and H₂S capture technologies thatutilize aqueous amine solutions are highly energy inefficient due to thehigh energy requirements for regeneration (e.g., 120° C.-140° C.).

Furthermore, aqueous amines are prone to foaming and are corrosive innature; often components and piping require stainless steel forconstruction. They also form non-regenerative, degradative compounds inthe system that need to be periodically removed. Moreover, with adsorbercolumns, regenerative columns, flash tanks, reboilers, and watertreatment systems, amine systems have a large equipment footprint andare typically not modular in design, making these acid gas removalsystems costly and unsuitable for many gas capture applications, such asoffshore use.

Solid CO₂ sorbents have shown many advantages over conventionalseparation technologies that utilize aqueous amine solvents. Forinstance, solid CO₂ sorbents have been shown to capture CO₂ under highpressure. Moreover, many solid CO₂ sorbents have lower regenerationenergy requirements, higher CO₂ uptake capacities, selectivity overhydrocarbons, and ease of handling. Moreover, solid CO₂ sorbents haveshown lower heat capacities, faster kinetics of sorption and desorption,and high mechanical strength. In addition, solid CO₂ sorbents have beenutilized to capture and release CO₂ without significant pressure andtemperature swings.

However, a limitation of many solid CO₂ sorbents is the cost ofproduction. Many solid CO₂ sorbents are also unable to compress andseparate CO₂ from the sorbents in an efficient manner. Moreover, the H₂Ssorption capacities of many solid CO₂ sorbents have not beenascertained. Therefore, a need exists for the development of moreeffective and affordable CO₂ and H₂S sorbents. A need also exists formore effective methods of utilizing such sorbents to capture CO₂ and H₂Sfrom various environments.

In some embodiments such as illustrated in FIG. 1, the presentdisclosure pertains to methods of capturing a gas from an environment.In some embodiments, the method includes associating the environmentwith a porous carbon material (step 10) to result in sorption of gascomponents (e.g., CO₂, H₂S, and combinations thereof) to the porouscarbon material (step 12). In some embodiments, the methods of thepresent disclosure also include a step of releasing the gas componentsfrom the porous carbon material (step 14). In some embodiments, themethods of the present disclosure also include a step of reusing theporous carbon material after the release of the gas components (step16). In some embodiments, the methods of the present disclosure alsoinclude a step of disposing the released gas components (step 18). Insome embodiments, the porous carbon material includes asphalt derivedporous carbon materials.

As set forth in more detail herein, the gas capture methods and porouscarbon materials of the present disclosure have numerous embodiments.For instance, various methods may be utilized to associate various typesof porous carbon materials with various environments to result in thecapture of various gas components from the environment. Moreover, thecaptured gas components may be released from the porous carbon materialsin various manners.

Environments

The methods of the present disclosure may be utilized to capture gasfrom various environments. In some embodiments, the environmentincludes, without limitation, industrial gas streams, natural gasstreams, natural gas wells, industrial gas wells, oil and gas fields,and combinations thereof. In some embodiments, the environment is asubsurface oil and gas field. In more specific embodiments, the methodsof the present disclosure may be utilized to capture gas from anenvironment that contains natural gas, such as an oil well.

In some embodiments, the environment is a pressurized environment. Forinstance, in some embodiments, the environment has a total pressurehigher than atmospheric pressure.

In some embodiments, the environment has a total pressure of about 0.1bar to about 500 bar. In some embodiments, the environment has a totalpressure of about 2.5 bar to about 100 bar. In some embodiments, theenvironment has a total pressure of about 5 bar to about 100 bar.

In some embodiments, the environment has a total pressure of about 25bar to about 30 bar. In some embodiments, the environment has a totalpressure of about 100 bar to about 200 bar. In some embodiments, theenvironment has a total pressure of about 200 bar to about 300 bar.

Gas Components

The methods of the present disclosure may be utilized to capture variousgas components from an environment. For instance, in some embodiments,the captured gas component includes, without limitation, CO₂, H₂S, andcombinations thereof. In some embodiments, the captured gas componentincludes CO₂. In some embodiments, the captured gas component includesH₂S. In some embodiments, the captured gas component includes CO₂ andH₂S.

Association of Porous Carbon Materials with an Environment

Various methods may be utilized to associate porous carbon materials ofthe present disclosure with an environment. In some embodiments, theassociation occurs by incubating the porous carbon materials with theenvironment (e.g., a pressurized environment). In some embodiments, theassociation of porous carbon materials with an environment occurs byflowing the environment through a structure that contains the porouscarbon materials. In some embodiments, the structure may be a column ora sheet that contains immobilized porous carbon materials. In someembodiments, the structure may be a floating bed that contains porouscarbon materials.

In some embodiments, the porous carbon materials are suspended in asolvent while being associated with an environment. In some embodiments,the solvent may include water or alcohol. In some embodiments, theporous carbon materials are associated with an environment in pelletizedform. In some embodiments, the pelletization can be used to assist flowof the gas component through the porous carbon materials.

In some embodiments, the associating occurs by placing the porous carbonmaterial at or near the environment. In some embodiments, such placementoccurs by various methods that include, without limitation, adhesion,immobilization, clamping, and embedding. Additional methods by which toassociate porous carbon materials with an environment can also beenvisioned.

Gas Sorption to Porous Carbon Materials

The sorption of gas components (e.g., CO₂, H₂S, and combinationsthereof) to porous carbon materials of the present disclosure can occurat various environmental pressures. For instance, in some embodiments,the sorption of gas components to porous carbon materials occurs aboveatmospheric pressure. In some embodiments, the sorption of gascomponents to porous carbon materials occurs at total pressures rangingfrom about 0.1 bar to about 500 bar. In some embodiments, the sorptionof gas components to porous carbon materials occurs at total pressuresranging from about 5 bar to about 500 bar. In some embodiments, thesorption of gas components to porous carbon materials occurs at totalpressures ranging from about 5 bar to about 100 bar. In someembodiments, the sorption of gas components to porous carbon materialsoccurs at total pressures ranging from about 25 bar to about 30 bar. Insome embodiments, the sorption of gas components to porous carbonmaterials occurs at total pressures ranging from about 100 bar to about500 bar. In some embodiments, the sorption of gas components to porouscarbon materials occurs at total pressures ranging from about 100 bar toabout 300 bar. In some embodiments, the sorption of gas components toporous carbon materials occurs at total pressures ranging from about 100bar to about 200 bar. In some embodiments, the sorption of gascomponents to porous carbon materials occurs at between atmosphericpressure and about 100 bar of total or partial pressure.

The sorption of gas components to porous carbon materials can also occurat various temperatures. For instance, in some embodiments, the sorptionof gas components to porous carbon materials occurs at temperatures thatrange from about 0° C. (e.g., a sea floor temperature where a wellheadmay reside) to about 100° C. (e.g., a temperature where machinery mayreside). In some embodiments, the sorption of gas components to porouscarbon materials occurs at ambient temperature (e.g., temperaturesranging from about 20-25° C., such as 23° C.). In some embodiments, thesorption of gas components to porous carbon materials occurs belowambient temperature. In some embodiments, the sorption of gas componentsto porous carbon materials occurs above ambient temperature. In someembodiments, the sorption of gas components to porous carbon materialsoccurs without the heating of the porous carbon materials. In someembodiments, the sorption of gas components to porous carbon materialsoccurs without the heating of the porous carbon materials or theenvironment.

Without being bound by theory, it is envisioned that the sorption of gascomponents to porous carbon materials occurs by various molecularinteractions between gas components (e.g., CO₂ or H₂S) and the porouscarbon materials. For instance, in some embodiments, the sorption of gascomponents to porous carbon materials occurs by at least one ofabsorption, adsorption, ionic interactions, physisorption,chemisorption, covalent bonding, non-covalent bonding, hydrogen bonding,van der Waals interactions, acid-base interactions, and combinations ofsuch mechanisms. In some embodiments, the sorption includes anabsorption interaction between gas components (e.g., CO₂ or H₂S) in anenvironment and the porous carbon materials. In some embodiments, thesorption includes an ionic interaction between the gas components in anenvironment and the porous carbon materials. In some embodiments, thesorption includes an adsorption interaction between the gas componentsin an environment and the porous carbon materials. In some embodiments,the sorption includes a physisorption interaction between the gascomponents in an environment and the porous carbon materials. In someembodiments, the sorption includes a chemisorption interaction betweenthe gas components in an environment and the porous carbon materials. Insome embodiments, the sorption includes a covalent bonding interactionbetween the gas components in an environment and the porous carbonmaterials. In some embodiments, the sorption includes a non-covalentbonding interaction between the gas components in an environment and theporous carbon materials. In some embodiments, the sorption includes ahydrogen bonding interaction between the gas components in anenvironment and the porous carbon materials. In some embodiments, thesorption includes a van der Waals interaction between the gas componentsin an environment and the porous carbon materials. In some embodiments,the sorption includes an acid-base interaction between the gascomponents in an environment and the porous carbon materials. In someembodiments, the sorption of gas components to porous carbon materialsoccurs by adsorption and absorption.

CO₂ Sorption

In some embodiments, the sorption of gas components to porous carbonmaterials includes the sorption of CO₂ to the porous carbon materials.In some embodiments, the sorption of CO₂ to porous carbon materialsoccurs at a partial CO₂ pressure of about 0.1 bar to about 100 bar. Insome embodiments, the sorption of CO₂ to porous carbon materials occursat a partial CO₂ pressure of about 5 bar to about 30 bar. In someembodiments, the sorption of CO₂ to porous carbon materials occurs at apartial CO₂ pressure of about 30 bar.

Without being bound by theory, it is envisioned that CO₂ sorption may befacilitated by various chemical reactions. For instance, in someembodiments, the sorbed CO₂ is converted to poly (CO₂) within the poresof the porous carbon materials. In some embodiments, the poly (CO₂)comprises the following formula: —(O—C(═O))_(n)—, where n is equal to orgreater than 2. In some embodiments, n is between 2 to 10,000. In someembodiments, the formed poly(CO₂) may be further stabilized by van derWaals interactions with the carbon surfaces in the pores of the carbonmaterials. In some embodiments, the formed poly(CO₂) may be in solidform. In some embodiments, the poly(CO₂) matrix can be formed in alayered structure where there is a stacked layering of the CO₂ where theCO₂ molecules have restricted tumbling and rotations due to an orderedstacked arrangement on the surface.

In some embodiments, the sorbed CO₂ may be converted to a matrix of CO₂within the pores of the porous carbon materials. In some embodiments,the matrix of CO₂ may be in the form of a matrix of ordered CO₂.

In some embodiments, the sorption of CO₂ to the porous carbon materialsoccurs selectively. For instance, in some embodiments, the sorption ofCO₂ to the porous carbon materials occurs selectively over hydrocarbonsin the environment (e.g., ethane, propane, butane, pentane, methane, andcombinations thereof). In further embodiments, the molecular ratio ofsorbed CO₂ to sorbed hydrocarbons in the porous carbon materials isgreater than about 2. In additional embodiments, the molecular ratio ofsorbed CO₂ to sorbed hydrocarbons in the porous carbon materials rangesfrom about 2 to about 10. In additional embodiments, the molecular ratioof sorbed CO₂ to sorbed hydrocarbons in the porous carbon materials isabout 8.

In more specific embodiments, the sorption of CO₂ to porous carbonmaterials occurs selectively over the CH₄ in the environment. In furtherembodiments, the molecular ratio of sorbed CO₂ to sorbed CH₄ (nCO₂/nCH₄)in the porous carbon materials is greater than about 2. In additionalembodiments, nCO_(2/)nCH₄ in the porous carbon materials ranges fromabout 2 to about 20. In some embodiments, nCO_(2/)nCH₄ in the porouscarbon materials ranges from about 2 to about 10. In more specificembodiments, nCO_(2/)nCH₄ in the porous carbon materials is about 20 at30 bar.

In some embodiments, sorption of CO₂ to porous carbon materials occursselectively through poly(CO₂) formation within the pores of the porouscarbon materials. Without being bound by theory, it is envisioned thatpoly(CO₂) formation within the pores of the porous carbon materials candisplace other gas components associated with the porous carbonmaterials, including any physisorbed gas components and hydrocarbons(e.g., methane, propane, and butane). Without being bound by furthertheory, it is also envisioned that the displacement of other gascomponents from the porous carbon materials creates a continual CO₂selectivity that far exceeds various CO₂ selectively ranges, includingthe CO₂ selectivity ranges noted above.

In some embodiments, the covalent or stacked dipolar nature of poly(CO₂)within the pores of the porous carbon materials can be 100 timesstronger than that of other physisorbed entities, including physisorbedgas components within the pores of the porous carbon materials.Therefore, such strong covalent bonds or dipolar bonds can contribute tothe displacement of the physisorbed gas components (e.g., methane,propane and butane). The dipolar bonds are arranged such that the oxygenof one CO₂ is donating into a lone pair electron density in the carbonatom of a neighboring CO₂. This pattern can repeat itself in a1-dimensional, 2-dimensional to 3-dimensional arrangement.

H₂S Sorption

In some embodiments, the sorption of gas components to porous carbonmaterials includes the sorption of H₂S to the porous carbon materials.In some embodiments, the sorption of H₂S to porous carbon materialsoccurs at a partial H₂S pressure of about 0.1 bar to about 100 bar. Insome embodiments, the sorption of H₂S to porous carbon materials occursat a partial H₂S pressure of about 5 bar to about 30 bar. In someembodiments, the sorption of H₂S to porous carbon materials occurs at apartial H₂S pressure of about 30 bar.

Without being bound by theory, it is envisioned that H₂S sorption may befacilitated by various chemical reactions. For instance, in someembodiments, sorbed H₂S may be converted within the pores of the porouscarbon materials to at least one of elemental sulfur (S), sulfur dioxide(SO₂), sulfuric acid (H₂SO₄), hydridosulfide (HS⁻), sulfide (S²⁻) andcombinations thereof. In some embodiments, the aforementioned conversioncan be facilitated by the presence of oxygen. For instance, in someembodiments, the introduction of small amounts of oxygen into a systemcontaining porous carbon materials can facilitate the conversion of H₂Sto elemental sulfur. In some embodiments, the oxygen can be introducedeither continuously or periodically. In some embodiments, the oxygen canbe introduced from air.

In some embodiments, the captured H₂S is converted by catalyticoxidation to elemental sulfur at ambient temperature. Thereafter,further oxidation to SO₂ and H₂SO₄ occurs at higher temperatures.

In some embodiments, nitrogen groups of porous carbon materials mayfacilitate the conversion of H₂S to elemental sulfur. For instance, insome embodiments illustrated in the schemes in FIG. 2, nitrogenfunctional groups on porous carbon materials may facilitate thedissociation of H₂S to HS⁻. In some embodiments, the nitrogen functionalgroups may also facilitate the formation of chemisorbed oxygen species(Seredych, M.; Bandosz, T. J. J. Phys. Chem. C 2008, 112, 4704-4711).

In some embodiments, the porous carbon material becomes impregnated withthe sulfur derived from captured H₂S to form sulfur-impregnated porouscarbon materials. In some embodiments, the formation ofsulfur-impregnated porous carbon materials may be facilitated byheating. In some embodiments, the heating occurs at temperatures higherthan H₂S capture temperatures. In some embodiments, the heating occursin the absence of oxygen. In some embodiments, the sulfur impregnatedporous carbon material can be used to efficiently capture CO₂ by theaforementioned methods.

In some embodiments, the sorption of H₂S to porous carbon materialsoccurs in intact form. In some embodiments, the sorption of H₂S toporous carbon materials in intact form occurs in the absence of oxygen.

CO₂ and H₂S Sorption

In some embodiments, the sorption of gas components to porous carbonmaterials includes the sorption of both H₂S and CO₂ to the porous carbonmaterials. In some embodiments, the sorption of H₂S and CO₂ to theporous carbon material occurs at the same time.

In some embodiments, the sorption of CO₂ to the porous carbon materialoccurs before the sorption of H₂S to the porous carbon material. Forinstance, in some embodiments, a gas containing CO₂ and H₂S flowsthrough a structure that contains porous carbon materials (e.g.,trapping cartridges). CO₂ is first captured from the gas as the gasflows through the structure. Thereafter, H₂S is captured from the gas asthe gas continues to flow through the structure.

In some embodiments, the sorption of H₂S to the porous carbon materialoccurs before the sorption of CO₂ to the porous carbon material. Forinstance, in some embodiments, a gas containing CO₂ and H₂S flowsthrough a structure that contains porous carbon materials (e.g.,trapping cartridges). H₂S is first captured from the gas as the gasflows through the structure. Thereafter, CO₂ is captured from the gas asthe gas continues to flow through the structure.

In some embodiments, the porous carbon materials that capture H₂S fromthe gas include nitrogen-containing porous carbon materials, asdescribed in more detail herein. In some embodiments, the porous carbonmaterials that capture CO₂ from the gas include sulfur-containing porouscarbon materials that are also described in more detail herein.

Release of Captured Gas

In some embodiments, the methods of the present disclosure also includea step of releasing captured gas components from porous carbonmaterials. Various methods may be utilized to release captured gascomponents from porous carbon materials. For instance, in someembodiments, the releasing occurs by decreasing the pressure of theenvironment. In some embodiments, the pressure of the environment isreduced to atmospheric pressure or below atmospheric pressure. In someembodiments, the releasing occurs by placing the porous carbon materialin a second environment that has a lower pressure than the environmentwhere gas capture occurred. In some embodiments, the second environmentmay be at or below atmospheric pressure. In some embodiments, thereleasing occurs spontaneously as the environmental pressure decreases.This is often referred to as pressure swing sorption or a pressure swingseparation process.

The release of captured gas components from porous carbon materials canoccur at various pressures. For instance, in some embodiments, therelease occurs at or below atmospheric pressure. In some embodiments,the release occurs at total pressures ranging from about 0 bar to about100 bar. In some embodiments, the release occurs at total pressuresranging from about 0.1 bar to about 50 bar. In some embodiments, therelease occurs at total pressures ranging from about 0.1 bar to about 30bar. In some embodiments, the release occurs at total pressures rangingfrom about 0.1 bar to about 10 bar. In some embodiments, the releaseoccurs at total pressures ranging from about 0.1 bar to aboutatmospheric pressure.

The release of captured gas components from porous carbon materials canalso occur at various temperatures. In some embodiments, the releasingoccurs at ambient temperature. In some embodiments, the releasing occursat the same temperature at which gas sorption occurred. In someembodiments, the releasing occurs without heating the porous carbonmaterials. In some embodiments, the releasing occurs without heating theporous carbon materials or the environment. Therefore, in someembodiments, a temperature swing is not required to release captured gascomponents from porous carbon materials.

In some embodiments, the releasing occurs at temperatures ranging fromabout 30° C. to about 200° C. In some embodiments, the releasing isfacilitated by also lowering the pressure.

In some embodiments, the releasing occurs by heating the porous carbonmaterials. In some embodiments, the releasing is enhanced by theaddition of heat to the porous carbon material or to the environment.For instance, in some embodiments, the releasing occurs by heating theporous carbon materials to temperatures between about 50° C. to about200° C. In some embodiments, the releasing occurs by heating the porouscarbon materials to temperatures between about 75° C. to about 125° C.In some embodiments, the releasing occurs by heating the porous carbonmaterials to temperatures ranging from about 50° C. to about 100° C. Insome embodiments, the releasing occurs by heating the porous carbonmaterials to a temperature of about 90° C.

In some embodiments, heat for release of gas components from porouscarbon materials can be supplied from various sources. For instance, insome embodiments, the heat for the release of gas components from aporous carbon material-containing vessel can be provided by an adjacentvessel whose heat is being generated during a gas sorption step.

In some embodiments, the release of captured gas components from anenvironment includes the release of captured CO₂ from porous carbonmaterials. Without being bound by theory, it is envisioned that therelease of captured CO₂ from porous carbon materials can occur byvarious mechanisms. For instance, in some embodiments, the release ofcaptured CO₂ can occur through a depolymerization of the formedpoly(CO₂) within the pores of the porous carbon materials. In someembodiments, the depolymerization can be facilitated by a decrease inenvironmental pressure. In some embodiments, the releasing of the CO₂occurs by decreasing the pressure of the environment or placing theporous carbon material in a second environment that has a lower pressurethan the environment where CO₂ capture occurred.

In some embodiments, the release of captured gas components from anenvironment includes the release of captured H₂S from porous carbonmaterials. In some embodiments, the captured H₂S is released in intactform.

In some embodiments, H₂S is released from porous carbon materials byheating the porous carbon materials. In some embodiments, H₂S isreleased from porous carbon materials by heating the porous carbonmaterials to temperatures that range from about 50° C. to about 200° C.In some embodiments, H₂S is released from the porous carbon materials byheating the porous carbon materials to temperatures between about 75° C.to about 125° C. In some embodiments, H₂S is released from the porouscarbon materials by heating the porous carbon materials to temperaturesbetween about 50° C. to about 100° C. In some embodiments, H₂S isreleased from the porous carbon materials by heating the porous carbonmaterials to a temperature of about 90° C.

In some embodiments, the release of captured H₂S can occur throughconversion of H₂S to at least one of elemental sulfur (S), sulfurdioxide (SO₂), sulfuric acid (H₂SO₄), hydridosulfide (HS⁻), sulfide(S²⁻) and combinations thereof. In some embodiments, elemental sulfur isretained on the porous carbon material to form sulfur-impregnated porouscarbon materials. In some embodiments, the sulfur-containing porouscarbon material can be discarded through incineration or burial. In someembodiments, the sulfur-impregnated porous carbon material can be usedfor the reversible capture of CO₂. In some embodiments, thesulfur-impregnated porous carbon material can be heated to hightemperature of 400-900° C. to make a sulfur-impregnated porous carbonused for the reversible capture of CO₂.

In some embodiments, the release of captured gas components can occur ina sequential manner. For instance, in some embodiments where the sorbedgas components include both CO₂ and H₂S, the releasing of the CO₂ occursby decreasing the pressure of the environment or placing the porouscarbon material in a second environment that has a lower pressure thanthe environment where CO₂ capture occurred. In some embodiments, thereleasing of the H₂S occurs by heating the porous carbon material (e.g.,at temperatures ranging from about 50° C. to about 100° C.). In someembodiments, the releasing of the CO₂ occurs before the releasing of theH₂S. In some embodiments, the releasing of the H₂S occurs before thereleasing of the CO₂. In some embodiments, the releasing of H₂S occursin an environment that lacks oxygen.

Disposal of the Released Gas

In some embodiments, the methods of the present disclosure also includea step of disposing the released gas components. For instance, in someembodiments, the released gas components can be off-loaded into acontainer. In some embodiments, the released gas components can bepumped downhole for long-term storage. In some embodiments, the releasedgas components can be vented to the atmosphere. In some embodiments, thereleased gas components include, without limitation, CO₂, H₂S, SO₂, andcombinations thereof.

Reuse of the Porous Carbon Material

In some embodiments, the methods of the present disclosure also includea step of reusing the porous carbon materials after gas componentrelease to capture more gas components from an environment. In someembodiments, the porous carbon materials of the present disclosure maybe reused over 100 times without substantially affecting their gassorption capacities. In some embodiments, the porous carbon materials ofthe present disclosure may be reused over 1000 times withoutsubstantially affecting their gas sorption capacities. In someembodiments, the porous carbon materials of the present disclosure maybe reused over 10,000 times without substantially affecting their gassorption capacities.

In some embodiments, the porous carbon materials of the presentdisclosure may retain 100 wt % of their CO₂ or H₂S sorption capacitiesafter being used multiple times (e.g., 100 times, 1,000 times or 10,000times). In some embodiments, the porous carbon materials of the presentdisclosure may retain at least 98 wt % of their CO₂ or H₂S sorptioncapacities after being used multiple times (e.g., 100 times, 1,000 timesor 10,000 times). In some embodiments, the porous carbon materials ofthe present disclosure may retain at least 95 wt % of their CO₂ or H₂Ssorption capacities after being used multiple times (e.g., 100 times,1,000 times or 10,000 times). In some embodiments, the porous carbonmaterials of the present disclosure may retain at least 90 wt % of theirCO₂ or H₂S sorption capacities after being used multiple times (e.g.,100 times, 1,000 times or 10,000 times). In some embodiments, the porouscarbon materials of the present disclosure may retain at least 80 wt %of their CO₂ or H₂S sorption capacities after being used multiple times(e.g., 100 times, 1,000 times or 10,000 times).

Porous Carbon Materials

Various porous carbon materials may be utilized to capture gas from anenvironment. In some embodiments, the present disclosure pertains to theporous carbon materials that are utilized to capture gas from anenvironment.

Carbon Sources

The porous carbon materials of the present disclosure may be derivedfrom various carbon sources. For instance, in some embodiments, theporous carbon material includes, without limitation, protein-derivedporous carbon materials, carbohydrate-derived porous carbon materials,cotton-derived porous carbon materials, fat-derived porous carbonmaterials, waste-derived porous carbon materials, asphalt-derived porouscarbon materials, coal-derived porous carbon materials, coke-derivedporous carbon materials, asphaltene-derived porous carbon materials, oilproduct-derived porous carbon materials, bitumen-derived porous carbonmaterials, tar-derived porous carbon materials, pitch-derived porouscarbon materials, anthracite-derived porous carbon materials,melamine-derived porous carbon materials, biochar-derived porous carbon,wood-derived porous carbon and combinations thereof.

In some embodiments, the porous carbon materials of the presentdisclosure include asphalt-derived porous carbon materials. In someembodiments, the porous carbon materials of the present disclosureinclude coal-derived porous carbon materials. In some embodiments, thecoal source includes, without limitation, bituminous coal, anthraciticcoal, brown coal, and combinations thereof.

In some embodiments, the porous carbon materials of the presentdisclosure include protein-derived porous carbon materials. In someembodiments, the protein source includes, without limitation, wheyprotein, rice protein, animal protein, plant protein, and combinationsthereof.

In some embodiments, the porous carbon materials of the presentdisclosure include oil product-derived porous carbon materials. In someembodiments, the oil products include, without limitation, petroleumoil, plant oil, and combinations thereof.

In some embodiments, the porous carbon materials of the presentdisclosure include waste derived porous carbon materials. In someembodiments, the waste can include, without limitation, human waste,animal waste, waste derived from municipality sources, and combinationsthereof.

The porous carbon materials of the present disclosure may also be invarious states. For instance, in some embodiments, the porous carbonmaterial is carbonized. In some embodiments, the porous carbon materialis reduced. In some embodiments, the porous carbon material isvulcanized.

Nucleophilic Moieties

In some embodiments, the porous carbon materials of the presentdisclosure include a plurality of nucleophilic moieties. In someembodiments, the porous carbon materials of the present disclosure maycontain various arrangements of nucleophilic moieties. In someembodiments, the nucleophilic moieties are part of the porous carbonmaterial. In some embodiments, the nucleophilic moieties are embeddedwithin the porous carbon materials. In some embodiments, thenucleophilic moieties are homogenously distributed throughout the porouscarbon material framework. In some embodiments, the nucleophilicmoieties are embedded within the plurality of the pores of the porouscarbon materials.

In some embodiments, the nucleophilic moieties include, withoutlimitation, primary nucleophiles, secondary nucleophiles, tertiarynucleophiles and combinations thereof. In some embodiments, thenucleophilic moieties include, without limitation, oxygen-containingmoieties, sulfur-containing moieties, metal-containing moieties, metaloxide-containing moieties, metal sulfide-containing moieties,nitrogen-containing moieties, phosphorous-containing moieties, andcombinations thereof.

In more specific embodiments, the nucleophilic moieties includephosphorous-containing moieties. In some embodiments, the phosphorouscontaining moieties include, without limitation, phosphines, phosphites,phosphine oxides, and combinations thereof.

In some embodiments, the nucleophilic moieties includenitrogen-containing moieties. In some embodiments, thenitrogen-containing moieties include, without limitation, primaryamines, secondary amines, tertiary amines, nitrogen oxides, pyridinicnitrogens, pyrrolic nitrogens, graphitic nitrogens, and combinationsthereof. In more specific embodiments, the nitrogen containing moietiesinclude nitrogen oxides, such as N-oxides.

In some embodiments, the nitrogen-containing moieties include from about1 wt % to about 15 wt % by weight of the porous carbon material. In someembodiments, the nitrogen-containing moieties include from about 2 wt %to about 11 wt % by weight of the porous carbon material. In someembodiments, the nitrogen-containing moieties include from about 5 wt %to about 9 wt % by weight of the porous carbon material. In someembodiments, the nitrogen-containing moieties include from about 8 wt %to about 11 wt % by weight of the porous carbon material. In someembodiments, the nitrogen-containing moieties include about 9 wt % byweight of the porous carbon material.

In some embodiments, the nucleophilic moieties include sulfur-containingmoieties. In some embodiments, the sulfur-containing moieties include,without limitation, primary sulfurs, secondary sulfurs, sulfur oxides,and combinations thereof.

In some embodiments, the nucleophilic moieties includenitrogen-containing moieties and sulfur-containing moieties. In someembodiments, the nitrogen-containing moieties and sulfur-containingmoieties induce CO₂ capture by poly(CO₂) formation. In some embodiments,the nitrogen-containing moieties induce H₂S capture by facilitatingoxidation of H₂S.

Surface Areas

The porous carbon materials of the present disclosure may have varioussurface areas. For instance, in some embodiments, the porous carbonmaterials of the present disclosure have surface areas that range fromabout 1,000 m²/g to about 4,500 m²/g. In some embodiments, the porouscarbon materials of the present disclosure have surface areas that rangefrom about 2,500 m²/g to about 4,500 m²/g. In some embodiments, theporous carbon materials of the present disclosure have surface areasthat range from about 2,500 m²/g to about 4,200 m²/g. In more specificembodiments, the porous carbon materials of the present disclosure havesurface areas that include at least one of 2,200 m² g⁻¹, 2,300 m²/g,2,600 m²/g, 2,800 m²/g, 2,900 m² g⁻¹ or 4,200 m² g⁻¹.

Porosities

In some embodiments, the porous carbon materials of the presentdisclosure include a plurality of pores. In addition, the porous carbonmaterials of the present disclosure may have various porosities. Forinstance, in some embodiments, the pores in the porous carbon materialsinclude diameters between about 1 nanometer to about 5 micrometers. Insome embodiments, the pores include macropores with diameters of atleast about 50 nm. In some embodiments, the pores include macroporeswith diameters between about 50 nanometers to about 3 micrometers. Insome embodiments, the pores include macropores with diameters betweenabout 500 nanometers to about 2 micrometers. In some embodiments, thepores include mesopores with diameters of less than 50 nm and largerthan about 2 nm. In some embodiments, the pores include micropores withdiameters of less than about 2 nm.

In some embodiments, the pores include diameters that range from about 1nm to about 10 nm. In some embodiments, the pores include diameters thatrange from about 1 nm to about 3 nm. In some embodiments, the poresinclude diameters that range from about 5 nm to about 100 nm. In someembodiments, the pores include diameters that are about 3 nm or less. Insome embodiments, the majority of the pores in the porous carbonmaterial include diameters that are about 3 nm or less.

In some embodiments, the porous carbon materials have a uniformdistribution of pore sizes. In some embodiments, the uniform pore sizesare about 1.3 nm in diameter.

The pores of the porous carbon materials of the present disclosure mayalso have various volumes. For instance, in some embodiments, the poresin the porous carbon materials have volumes ranging from about 1 cm³/gto about 10 cm³/g. In some embodiments, the pores in the porous carbonmaterials have volumes ranging from about 1 cm³/g to about 3 cm³/g. Insome embodiments, the pores in the porous carbon materials have volumesranging from about 1 cm³/g to about 1.5 cm³/g. In more specificembodiments, the plurality of pores in the porous carbon materials havevolumes of about 1.1 cm³/g, about 1.2 cm³/g, or about 1.4 cm³/g.

Densities

The porous carbon materials of the present disclosure may also havevarious densities. For instance, in some embodiments, the porous carbonmaterials of the present disclosure have densities that range from about0.3 g/cm³ to about 10 g/cm³. In some embodiments, the porous carbonmaterials of the present disclosure have densities that range from about0.3 g/cm³ to about 4 g/cm³. In some embodiments, the porous carbonmaterials of the present disclosure have densities that range from about1 g/cm³ to about 3 g/cm³. In some embodiments, the porous carbonmaterials of the present disclosure have densities that range from about1 g/cm³ to about 2.5 g/cm³. In some embodiments, the porous carbonmaterials of the present disclosure have densities that range from about2 g/cm³ to about 3 g/cm³. In more specific embodiments, the porouscarbon materials of the present disclosure have densities of 1.8 g/cm³,2 g/cm³, or 2.2 g/cm³.

CO₂ Sorption Capacities

The porous carbon materials of the present disclosure may also havevarious sorption capacities. For instance, in some embodiments, theporous carbon materials of the present disclosure have a CO₂ sorptioncapacity (also referred to as CO₂ uptake) that ranges from about 10 wt %to about 150 wt % of the porous carbon material weight. In someembodiments, the porous carbon materials of the present disclosure havea CO₂ sorption capacity of about 50 wt % to about 150 wt % of the porouscarbon material weight. In some embodiments, the porous carbon materialsof the present disclosure have a CO₂ sorption capacity of about 50 wt %to about 100 wt % of the porous carbon material weight. In someembodiments, the porous carbon materials of the present disclosure havea CO₂ sorption capacity of about 50 wt % to about 200 wt % of the porouscarbon material weight. In some embodiments, the porous carbon materialsof the present disclosure have a CO₂ sorption capacity of about 100 wt %to about 150 wt % of the porous carbon material weight. In more specificembodiments, the porous carbon materials of the present disclosure havea CO₂ sorption capacity of about 120 wt % to about 130 wt % of theporous carbon material weight.

In further embodiments, the porous carbon materials of the presentdisclosure have a CO₂ sorption capacity of about 0.5 g to about 2 g ofCO₂ per 1 g of porous carbon material. In some embodiments, the porouscarbon materials of the present disclosure have a CO₂ sorption capacityof about 1 g to about 2 g of CO₂ per 1 g of porous carbon material. Insome embodiments, the porous carbon materials of the present disclosurehave a CO₂ sorption capacity of about 1.2 g to about 1.3 g of CO₂ per 1g of porous carbon material.

In further embodiments, the porous carbon materials of the presentdisclosure have a CO₂ sorption capacity of about 0.6 g to about 2.0 g ofCO₂ per 1 g of porous carbon material. In some embodiments, the porouscarbon materials of the present disclosure have a CO₂ sorption capacityof about 1 g to about 1.2 g of CO₂ per 1 g of porous carbon material. Insome embodiments, the porous carbon materials of the present disclosurehave a CO₂ sorption capacity of about 1.2 g of CO₂ per 1 g of porouscarbon material. In some embodiments, the porous carbon materials of thepresent disclosure have a CO₂ sorption capacity of about 0.92 g of CO₂per 1 g of porous carbon material. In some embodiments, the porouscarbon materials of the present disclosure have a CO₂ sorption capacityof about 0.92 g of CO₂ per 1 g of porous carbon material at a CO₂pressure or partial pressure of about 30 bar.

H₂S Sorption Capacities

The porous carbon materials of the present disclosure may also havevarious H₂S sorption capacities. For instance, in some embodiments, theporous carbon materials of the present disclosure have a H₂S sorptioncapacity that ranges from about 10 wt % to about 300 wt % of the porouscarbon material weight. In some embodiments, the porous carbon materialsof the present disclosure have a H₂S sorption capacity of about 50 wt %to about 300 wt % of the porous carbon material weight. In someembodiments, the porous carbon materials of the present disclosure havea H₂S sorption capacity of about 50 wt % to about 250 wt % of the porouscarbon material weight. In some embodiments, the porous carbon materialsof the present disclosure have a H₂S sorption capacity of about 100 wt %to about 250 wt % of the porous carbon material weight. In more specificembodiments, the porous carbon materials of the present disclosure havea H₂S sorption capacity of about 100 wt % to about 150 wt % of theporous carbon material weight. In some embodiments, Applicant has beenable to achieve uptake of 205 wt % H₂S sorption capacity using theasphalt doped porous carbon materials of the present disclosure.

In further embodiments, the porous carbon materials of the presentdisclosure have a H₂S sorption capacity of about 0.5 g to about 3 g ofsulfur from H₂S per 1 g of porous carbon material. In some embodiments,the porous carbon materials of the present disclosure have a H₂Ssorption capacity of about 0.5 g to about 2.5 g of sulfur from H₂S per 1g of porous carbon material. In some embodiments, the porous carbonmaterials of the present disclosure have a H₂S sorption capacity ofabout 1 g to about 2.5 g of sulfur from H₂S per 1 g of porous carbonmaterial. In some embodiments, the porous carbon materials of thepresent disclosure have a H₂S sorption capacity of about 1 g to about1.5 g of sulfur from H₂S per 1 g of porous carbon material.

Physical States

The porous carbon materials of the present disclosure may be in variousstates. For instance, in some embodiments, the porous carbon materialsof the present disclosure may be in a solid state. In some embodiments,the porous carbon materials of the present disclosure may be in agaseous state. In some embodiments, the porous carbon materials of thepresent disclosure may be in a liquid state.

Methods of Forming Porous Carbon Materials

In some embodiments, the present disclosure pertains to methods offorming the porous carbon materials of the present disclosure. In someembodiments, methods include carbonizing a carbon source to form porouscarbon materials and may also include a step of doping the carbonsource. In some embodiments, the methods of the present disclosure alsoinclude a step of vulcanizing the carbon source. In some embodiments,the methods of the present disclosure also include a step of reducingthe formed porous carbon material. In some embodiments, by pre-treatingthe carbon source prior to carbonization, no further treatment of theporous carbon is necessary.

As set forth in more detail herein, various methods may be utilized tocarbonize various types of carbon sources. In addition, various methodsmay be utilized to dope and vulcanize the carbon sources. Likewise,various methods may be utilized to reduce the formed porous carbonmaterials.

Carbon Sources

Various carbon sources may be utilized to form porous carbon materials.Suitable carbon sources were described previously. In some embodiments,the carbon sources include, without limitation, protein, carbohydrates,cotton, fat, waste, asphalt, coal, coke, asphaltene, oil products,bitumen, tar, pitch, anthracite, melamine, and combinations thereof.

In some embodiments, the carbon source includes asphalt. In someembodiments, the carbon source includes coal. In some embodiments, thecoal source includes, without limitation, bituminous coal, anthraciticcoal, brown coal, and combinations thereof. In some embodiments, thecarbon source includes protein. In some embodiments, the protein sourceincludes, without limitation, whey protein, rice protein, animalprotein, plant protein, and combinations thereof.

In some embodiments, the carbon source includes oil products. In someembodiments, the oil products include, without limitation, petroleumoil, plant oil, and combinations thereof.

Carbonizing

In the present disclosure, carbonization generally refers to processesor treatments that convert a carbon source (e.g., a non-porous carbonsource) to a porous carbon material. Various methods and conditions maybe utilized to carbonize carbon sources.

For instance, in some embodiments, the carbonizing occurs in the absenceof a solvent. In some embodiments, the carbonizing occurs in thepresence of a solvent.

In some embodiments, the carbonizing occurs by exposing the carbonsource to a carbonizing agent. In some embodiments, the carbonizingagent includes metal hydroxides or metal oxides. In some embodiments,the carbonizing agent includes, without limitation, potassium hydroxide(KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH), cesiumhydroxide (CsOH), magnesium hydroxide (Mg(OH)₂), calcium hydroxide(Ca(OH)₂), and combinations thereof. In some embodiments, thecarbonizing agent includes potassium hydroxide (KOH). In someembodiments, the carbonizing agent can be a metal oxide. In someembodiments, the metal oxide includes, without limitation, calcium oxide(CaO), magnesium oxide (MgO), and combinations thereof. In someembodiments, the weight ratio of the carbon source to the carbonizingagent varies from about 1:1 to about 1:5. In some embodiments, theweight ratio of the carbon source to the carbonizing agent is about 1:4.

In some embodiments, the carbonizing occurs by grinding the carbonsource in the presence of a carbonizing agent. In some embodiments, thegrinding occurs in a mortar. In some embodiments, the grinding includesball milling. In some embodiments, the grinding results in the formationof a homogenous solid powder.

In some embodiments, the carbon source and the carbonizing agent can bemixed in a solvent. In some embodiments, the solvent is evaporated aftermixing. In some embodiments, the evaporation is followed by thecarbonization of the carbon source at elevated temperature. In someembodiments, the carbon source is the solvent, and the carbonizing agentis added prior to carbonization at elevated temperatures.

In some embodiments, the carbonizing occurs by heating the carbon sourceat temperatures ranging from about 200° C. to about 1000° C. In someembodiments, the heating occurs at temperatures greater than 500° C. Insome embodiments, the heating occurs at temperatures of about 500° C. toabout 1000° C. In some embodiments, the heating occurs at temperaturesof about 600° C. to about 900° C. In some embodiments, the carbon sourceis pre-treated at a temperature between 300° C. to 400° C. to removevolatile oils from the carbon source. For instance, FIG. 31 shows thesuccessful removal of volatile oils by pre-treatment, as measured usingTGA.

In some embodiments, it is also possible to separate these oils from thecarbon source at lower temperatures using a reduced pressure atmosphere.After the removal of volatiles, the carbon source can subsequently behomogenized with potassium hydroxide and then heated to temperaturesgreater than 600° C. For example, by pre-treating asphalt at 400° C.prior to carbonizing with KOH, the resultant porous carbon has very highCO₂ uptake, matching or exceeding the performance of A-NPC and A-rNPC.Furthermore, pre-treated asphalt-derived porous carbons show an increasein CO₂ selectivity. No additives are required to achieve theaforementioned increased CO₂ uptake and selectivity.

In some embodiments, the carbonizing occurs in an inert atmosphere. Insome embodiments, the inert atmosphere includes a steady flow of aninert gas, such as argon.

Doping

In some embodiments, the methods of the present disclosure also includea step of doping a carbon source with a dopant. In some embodiments, thedopant includes, without limitation, nitrogen-containing dopants,sulfur-containing dopants, heteroatom-containing dopants,oxygen-containing dopants, sulfur-containing dopants, metal-containingdopants, metal oxide-containing dopants, metal sulfide-containingdopants, phosphorous-containing dopants, and combinations thereof.

In some embodiments, the dopant includes nitrogen-containing dopants. Insome embodiments, the nitrogen-containing dopants include, withoutlimitation, primary amines, secondary amines, tertiary amines, nitrogenoxides, pyridinic nitrogens, pyrrolic nitrogens, graphitic nitrogens,and combinations thereof. In some embodiments, the nitrogen-containingdopant includes NH₃.

In some embodiments, the dopant includes sulfur-containing dopants. Insome embodiments, the sulfur-containing dopants include, withoutlimitation, primary sulfurs, secondary sulfurs, sulfur oxides, andcombinations thereof. In some embodiments, the sulfur-containing dopantsinclude H₂S.

In some embodiments, the dopants include monomers, such asnitrogen-containing monomers. In some embodiments, the monomers aresubsequently polymerized.

Doping can occur at various temperatures. For instance, in someembodiments, the doping occurs at temperatures ranging from about 200°C. to about 800° C. In some embodiments, the doping occurs attemperatures ranging from about 600° C. to about 700° C. In someembodiments, the doping occurs at about 650° C. to about 700° C.

Various amounts of dopants may be utilized. For instance, in someembodiments, the weight ratio of the dopant to the carbon source variesfrom about 0.2:1 to about 1:1. In some embodiments, the weight ratio ofthe dopant to the carbon source is about 1:1.

Vulcanization

In some embodiments, the methods of the present disclosure also includea step of vulcanizing the carbon source. In some embodiments, thevulcanizing includes exposing the carbon source to a vulcanizing agent.In some embodiments, the vulcanizing agent includes, without limitation,sulfur-based agents, peroxides, urethane cross-linkers, metallic oxides,acetoxysilane, and combinations thereof. In some embodiments, thevulcanizing agent includes, without limitation, tetramethyldithiuram,2,2′-dithiobis(benzothiazole), and combinations thereof.

Various amounts of vulcanizing agents may be utilized. For instance, insome embodiments, the weight ratio of the vulcanization agent to thecarbon source varies from about 5 wt % to about 200 wt % relative to thecarbon source.

Reduction

In some embodiments, the methods of the present disclosure include astep of reducing the formed porous carbon material. In some embodiments,the reducing occurs by exposing the formed porous carbon material to areducing agent. In some embodiments, the reducing agent includes,without limitation, H₂, NaBH₄, hydrazine, and combinations thereof. Insome embodiments, the reducing agent includes H₂.

The methods of the present disclosure may be utilized to make bulkquantities of porous carbon materials. For instance, in someembodiments, the methods of the present disclosure can be utilized tomake porous carbon materials in quantities greater than about 1 g. Insome embodiments, the methods of the present disclosure can be utilizedto make porous carbon materials in quantities greater than about 1 kg.In some embodiments, the methods of the present disclosure can beutilized to make porous carbon materials in quantities greater thanabout 1000 kg.

In some embodiments, the porous carbon materials of the presentdisclosure are produced from a high fixed carbon content precursor thatincludes, without limitation, biochar, hydrochar, coal, lignite,biomass, organic substances containing heteroatoms such as nitrogen orsulfur, and combinations thereof. In some embodiments, the precursor isheated at temperatures greater than 600° C. In some embodiments, CO₂selectivity and CO₂ capacity of the porous carbon material is enhancedby functionalization of the porous carbon material surface during suchheating. In some embodiments, the precursor is activated at atemperature between about 650° C. and about 1000° C. in the presence ofan amount of activating agent in order to create and maintain microporeswithin the porous carbon material.

Advantages

The gas capture methods and the porous carbon materials of the presentdisclosure provide numerous advantages over prior gas sorbents. Forinstance, the porous carbon materials of the present disclosure providesignificantly higher CO₂ and H₂S sorption capacities than priorsorbents. Moreover, due to the availability and affordability of thestarting materials, the porous carbon materials of the presentdisclosure can be made in a facile and economical manner in bulkquantities. Furthermore, unlike traditional gas sorbents, the porouscarbon materials of the present disclosure can selectively capture andrelease CO₂ and H₂S at ambient temperature without requiring atemperature swing. As such, the porous carbon materials of the presentdisclosure can avoid substantial thermal degradation and be usedeffectively over successive cycles without losing their original CO₂ andH₂S sorption capacities.

Accordingly, the gas capture methods and the porous carbon materials ofthe present disclosure can find numerous applications. For instance, insome embodiments, the gas capture methods and the porous carbonmaterials of the present disclosure can be utilized for the capture ofCO₂ and H₂S from subsurface oil and gas fields. In more specificembodiments, the process may take advantage of differential pressurescommonly found in natural gas collection and processing streams as adriving force during CO₂ and H₂S capture. For instance, in someembodiments, the methods of the present disclosure may utilize a naturalgas-well pressure (e.g., a natural gas well pressure of 200 to 300 bar)as a driving force during CO₂ and H₂S capture. Thereafter, by loweringthe pressure back to ambient conditions after CO₂ and H₂S uptake, thecaptured gas can be off-loaded or pumped back downhole into thestructures that had held it for geological timeframes. Moreover, the gascapture methods and the porous carbon materials of the presentdisclosure can allow for the capture and reinjection of CO₂ and H₂S atthe natural gas sites, thereby leading to greatly reduced CO₂ and H₂Semissions from natural gas streams.

In some embodiments, the methods of the present disclosure can beutilized for the selective release of captured CO₂ and H₂S. Forinstance, in some embodiments where a porous carbon material hascaptured both CO₂ and H₂S, the lowering of environmental pressure canresult in the release of CO₂ from the porous carbon material and theretainment of the captured H₂S from the porous carbon material.Thereafter, the captured H₂S may be released from the porous carbonmaterial by heating the porous carbon material (e.g., at temperaturesbetween about 50° C. to about 100° C.). In additional embodiments wherea porous carbon material has captured both CO₂ and H₂S, the heating ofthe porous carbon material (e.g., at temperatures between about 50° C.to about 100° C.) can result in the release of the captured H₂S and theretainment of the captured CO₂. Thereafter, the lowering ofenvironmental pressure can result in the release of CO₂ from the porouscarbon.

Reference will now be made to more specific embodiments of the presentdisclosure and experimental results that provide support for suchembodiments. However, Applicants note that the disclosure below is forillustrative purposes only and is not intended to limit the scope of theclaimed subject matter in any way.

Example 1 Capture of CO₂ by Sulfur- and Nitrogen-Containing PorousCarbons

In this Example, nucleophilic porous carbons are synthesized from simpleand inexpensive carbon-sulfur and carbon-nitrogen precursors. Infrared,Raman and 13C nuclear magnetic resonance signatures substantiate CO₂fixation by polymerization in the carbon channels to form poly(CO₂)under much lower pressures than previously required. This growingchemisorbed sulfur- or nitrogen-atom-initiated poly(CO₂) chain furtherdisplaces physisorbed hydrocarbon, providing a continuous CO₂selectivity. Once returned to ambient conditions, the poly(CO₂)spontaneously depolymerizes, leading to a sorbent that can be easilyregenerated without the thermal energy input that is required fortraditional sorbents.

More specifically, Applicants show in this Example that the new carbonmaterials can be used to separate CO₂ from various environments (e.g.,natural gas), where 0.82 g of CO₂ per g of sorbent (82 wt %) can becaptured at 30 bar. A mechanism is described where CO₂ is polymerized inthe channels of the porous carbon materials, as initiated by the sulfuror nitrogen atoms that are part of the carbon framework. Moreover, notemperature swing is needed. The reaction proceeds at ambienttemperature. Without being bound by theory, it is envisioned that heattransfer between cylinders during the exothermic sorption andendothermic desorption can provide the requisite thermodynamicexchanges.

In some instances, the process can use the natural gas-well pressure of200 to 300 bar as a driving force during the polymerization. By loweringthe pressure back to ambient conditions after CO₂ uptake, the poly(CO₂)is then depolymerized, where it can be off-loaded or pumped backdownhole into the structures that had held it for geological timeframes.

Example 1.1 Synthesis and Characterization of Porous Carbons

Sulfur- and nitrogen-containing porous carbons (SPC and NPC,respectively) were prepared by treating bulk precursor polymers withpotassium hydroxide (KOH) at 600° C., as described previously (Carbon44, 2816-2821 (2006); Carbon 50, 5543-5553 (2012)).

As shown in FIG. 3A, the resulting products were solid porous carbonmaterials with homogeneously distributed sulfur or nitrogen atomsincorporated into the carbon framework. They exhibited pores and channelstructures as well as high surface areas of 2500 and 1490 m²/g (N₂,Brunauer-Emmett-Teller) for the SPC and the NPC, respectively, with porevolumes of 1.01 cm 3 g⁻¹ and 1.40 cm³ g, respectively. The scanningelectron microscopy (SEM) and transmission electron microscopy (TEM)images are shown in FIGS. 3B-D, and the X-ray photoelectron spectroscopy(XPS) analyses are shown in FIG. 4.

Example 1.2 CO₂ Uptake Measurements

For CO₂ uptake measurements, samples were analyzed using volumetricanalysis instruments. The measurements were further confirmed withgravimetric measurements.

FIG. 5 shows the pressure-dependent CO₂ excess uptake for the SPCsorbent at different temperatures peaking at 18.6 mmol CO₂ g⁻¹ ofsorbent (82 wt %) when at 22° C. and 30 bar. The sorption resultsmeasured by volumetric and gravimetric analyses were comparable, as werethose measurements on the two volumetric instruments.

Applicants chose 30 bar as the upper pressure limit in experimentsbecause a 300 bar well-head pressure at 10 mol % CO₂ concentration wouldhave a CO₂ partial pressure of 30 bar. FIGS. 5B-D show three consecutiveCO₂ sorption-desorption cycles on SPC over a pressure range from 0 to 30bar, which indicates that the SPC could be regenerated using a pressureswing process while retaining its original CO₂ sorption capacity.

In the case of microporous materials with negligible external surfacearea, total uptake is often used as an approximation for absoluteuptake, and the two values here are within 10% of each other. Forexample, the absolute CO₂ uptake of the SPC was 20.1 and 13.9 mmol/gunder 30 bar at 22° and 50° C., respectively. See FIGS. 6-7 and Example1.8.

Similarly, although absolute adsorption isotherms can be used todetermine the heat of sorption, excess adsorption isotherms are moreoften used to calculate the heat of CO₂ sorption (QCO₂) before thecritical point of the gas. Thus, the excess CO₂ sorption isothermsmeasured at two different temperatures, 23° C. and 50° C. (FIG. 5E),were input into the Clausius-Clapeyron equation. At lower surfacecoverage (≦1 bar), which could be expected to be more indicative of thesorbate-sorbent interaction, the SPC exhibits a heat of CO₂ sorption of57.8 kJ/mol⁻¹. Likewise, the maximum QCO₂ values for nucleophile-freeporous materials, such as activated carbon, Zeolite 5A and zeoliticimidazolate framework (ZIF-8, a class of the MOF) were measured to be28.4, and 31.2, 25.6 kJ/mol, respectively, at low surface coverage (seeExample 1.9). Based on this data, the SPC possesses the highest CO₂sorption enthalpy among these complementary sorbents measured at lowsurface coverage.

In order to better assess the sorption mechanism during the CO₂ uptake,attenuated total reflectance infrared spectroscopy (ATR-IR) was used tocharacterize the properties of the sorbents before and after the CO₂uptake. A sample vial with ˜100 mg of the SPC was loaded into a 0.8 Lstainless steel autoclave equipped with a pressure gauge and valves.Before the autoclave was sealed, the chamber was flushed with CO₂(99.99%) to remove residual air, and the system was pressurized to 10bar (line pressure limitation). The sorbent was therefore isobaricallyexposed to CO₂ in the closed system at 23° C. After 15 min, the systemwas vented to nitrogen at ambient pressure and the sorbent vial wasimmediately removed from the chamber and the sorbent underwent ATR-IRand Raman analyses in air.

FIGS. 8A-B show the ATR-IR spectra of the SPC before (black line) andafter exposure to 10 bar of CO₂, followed by ambient conditions for theindicated times. The two regions that appear in the ATR-IR spectra(outlined by the dashed-line boxes) after the CO₂ sorption are ofinterest. The first IR peak, located at 2345 cm⁻¹, is assigned to theanti-symmetric CO₂ stretch, confirming that CO₂ was physisorbed andevolving from the SPC sorbent. The other IR band, centered at 1730 cm⁻¹,is attributed to the C═O symmetric stretch from the poly(CO₂) on theSPC. Interestingly, this carbonyl peak is only observed with the porousheteroatom-doped carbon, such as the SPC and NPC. Other porous sorbentswithout nucleophilic species, such as ZIF-8 and activated carbon, onlyshowed the physisorbed or evolving CO₂ peak (2345 cm⁻¹) (FIGS. 9-10).Once the CO₂-filled SPC returned to ambient pressure, the key IR peaksattenuated over time and disappeared after 20 min. Based on this data,the ATR-IR study confirmed the poly(CO₂) formation. Raman spectroscopywas further used to probe individual chemical bond vibrations, as shownin FIG. 8C. The carbonaceous graphitic G-band and defect-deriveddiamonoid D-band were at 1590 and 1350 cm⁻¹. The peak at 798 cm⁻¹ can beattributed to the symmetric stretch of the C—O—C bonds, which was notobserved for the other nucleophile-free porous materials, suggestingthat the poly(CO₂), with the —(O—C(═O))n-moiety, was formed.

Without being bound by theory, it is envisioned that themonothiocarbonate and carbamate anions within the channels of the SPCand NPC, respectively, were the likely initiation points for the CO₂polymerization since no poly(CO₂) was seen in activated carbon (FIG.10). Furthermore, 13C NMR also confirms the presence of the poly(CO₂)formation. The sorbent gives a broad signal characteristic of aromaticcarbon (FIG. 8D, bottom).

After exposure to CO₂, a relatively sharp signal on top of the broadsorbent signal appears at 130.6 ppm, which can be assigned to the CO₂that is evolving from the support. A sharp signal also appears at 166.5ppm (FIG. 8D, middle) that is characteristic of the carbonyl resonancefor poly(CO₂). Both of these signals are gone 19 h later (FIG. 8D, top).These assignments are further discussed in detail in Example 1.10.

Compared to secondary amine-based CO₂ sorbents where maximum captureefficiency is 0.5 mol CO₂ per mol N (₂RNH₂+CO₂→RNH₂+—O₂CNHR), the SPCand NPC demonstrate a unique mechanism during the CO₂ uptake processresulting in their remarkably higher CO₂ capacities versus S or Ncontent (8.1 atomic % of S and 6.2 atomic % of N in the SPC and NPC,respectively, by XPS analysis).

FIGS. 8E and 8F show illustrations of the aforementioned CO₂-fixation bypolymerization. Dimeric CO₂ uptake has been crystallographicallyobserved in metal complexes, and polymeric CO₂ has been detectedpreviously but only at extremely high pressures of ˜15,000 bar. Thespectroscopic determination here confirms poly(CO₂) formation at muchlower pressures than formerly observed.

A series of porous materials with and without the nucleophilicheteroatoms were tested to compare their CO₂ capture performance up to30 bar at 30° C. (FIG. 10A). The SPC had the highest CO₂ capacity. TheNPC, activated carbon, zeolite 5A and ZIF-8 had lower capacities.Although NPC had lower CO₂ capacity than SPC, its uptake performancecould be improved by 21 wt % after H₂ reduction at 600° C., producingreduced-NPC (R-NPC) with secondary amine groups (FIG. 3A).

Even though the surface area of R-NPC (1450 m² g) is only slightlygreater than that of the activated carbon (1430 m² g), the presence ofthe amine groups induces the formation of the poly(CO2) under pressure,promoting the CO₂ sorption efficiency of the R-NPC. The pore volume ofR-NPC is 1.43 cm³ g.

Purification of natural gas from wells relies upon a highlyCO₂-selective sorbent, especially in a CH₄-rich environment. Thus, CH₄uptake experiments were carried out on three different types of porousmaterials, SPC, activated carbon and ZIF-8. FIGS. 11B-D compare CO₂ andCH₄ sorption over a pressure range from 0 to 30 bar at 23° C. Incontrast to the CO₂ sorption, the CH₄ isotherms for these three sorbentsreached equilibrium while the system pressure was approaching 30 bar.The order of the CH₄ uptake capacities was correlated to the surfacearea of the sorbents. Comparing these sorbents, the observed molecularratio of sorbed CO₂ to CH₄ (nCO2/nCH4) for the SPC (2.6) was greaterthan that for the activated carbon (1.5) and ZIF-8 (1.9). In addition,the density of the SPC calculated using volumetric analysis is nearly6-fold higher than in the ZIF-8 (2.21 vs. 0.35 g/cm³) and 3-fold higherthan the zeolite 5A (2.21 vs. 0.67 g/cm³). The high CO₂ capacity andhigh density observed for SPC greatly increase the volume efficiency,which would reduce the volume of the sorption material for a given CO₂uptake production rate.

In order to mimic a gas well environment and further characterize theSPC's selectivity to CO₂, a premixed gas (85 mol % CH₄, 10 mol % CO₂, 3mol % C₂H₆ and 2 mol % C₃H₈) was used with quadropole mass spectrometry(MS) detection. The MS inlet was connected to the gas uptake system sothat it could monitor the gas effluent from the SPC throughout thesorption-desorption experiment. FIG. 12 shows the mass spectrum recordedduring the sorption process. The peaks at 15 and 16 amu correspond tofragment and molecular ions from CH₄, while the peaks at 28 and 44 amuare from CO₂ in the premixed gas. Other minor peaks can be assigned tofragment ions from C₂H₆ and C₃H₈. Although the peak at 44 amu can alsocome from C₃H₈ ions, the contribution is negligible because of the lowerC₃H₈ concentration in the mixed gas, and it is distinguishable by thefragmentation ratios in the MS [C₃H₈: m/z=29 (100), 44 (30); CO₂:m/z=44(100), 28(11)]. The observed intensity ratio of two peaks at 16and 44 amu (116/144=9.1) indicates the abundance of CH₄ vs. CO₂ duringthe sorption and also reflects the relative amount of CH₄ and CO₂ in thepremixed gas. Once the sorption reached equilibrium under 30 bar, thedesorption process was induced by slowly venting into the MS system. The116/144 ratio reduced to ˜0.7. The SPC has been shown to have 2.6-foldhigher CO₂ than CH₄ affinity at 30 bar when using pure CO₂ and CH₄ asfeed gases (FIG. 11B).

If the binding energy of CH₄ and CO₂ were assumed to be similar, and thepartial pressure of CH₄ vs. CO₂ in the premixed gas is considered(PCH₄/PCO₂=8.5), then it is envisioned that the number of sorbed CH₄should be about 3.3 times more than that of the sorbed CO₂. It is alsoenvisioned that CO₂-selective materials have selective sites and oncethe CO₂ occupies those sites, the selectivity significantly decreasesand the materials behave as physisorbents with lower selectivities atlarger pressures. On the contrary, here the SPC demonstrates much higherCO₂ selectivity than expected since the chemisorbed sulfur-initiatedpoly(CO₂) chain displaces physisorbed gas.

Under the mechanism described here for CO₂ polymerization in thechannels of inexpensive nucleophilic porous carbons, these new materialshave continuous selectivity toward CO₂, limited only by the availablepore space and pressure.

Example 1.3 Instrumentations

An automated Sieverts instrument (Setaram PCTPro) was adopted to measuregas (CO₂, CH₄ or premixed gas) sorption properties of materials.Typically, a ˜70 mg of sorbent was packed into a ˜1.3 mL of stainlesssteel sample cell. The sample was pretreated under vacuum (˜3 mm Hg) at130° C. for 6 h and the sample volume was further determined by heliumbefore the uptake experiment. At each step of the measurement, testinggas was expanded from the reference reservoir into the sample cell untilthe system pressure reached equilibrium. A quadropole mass spectrometer(Setaram RGA200) was connected to the Sieverts instrument so that itcould monitor the gas effluent from the sorbent throughout the entiresorption-desorption experiment. With the assistance of a hybridturbomolecular drag pump, the background pressure of the MS can becontrolled lower than 5×10−8 Torr. All material densities weredetermined using volumetric analysis on this same instrument.

XPS was performed using a PHI Quantera SXM Scanning X-ray Microprobewith a base pressure of 5×10⁻⁹ Torr. Survey spectra were recorded in 0.5eV step size and a pass energy of 140 eV. Elemental spectra wererecorded in 0.1 eV step size and a pass energy of 26 eV. All spectrawere standardized using C1s peak (284.5 eV) as a reference.

The ATR-IR experiment was conducted using a Fourier transform infraredspectrometer (Nicolet Nexus 670) equipped with an attenuated totalreflectance system (Nicolet, Smart Golden Gate) and a MCT-A detector.Raman spectra were measured using a Renishaw in Via Raman Microscopewith a 514 nm excitation argon laser.

Scanning electron microscope (SEM) images were taken at 15 KeV using aJEOL-6500F field emission microscope. High-resolution transmissionelectron microscope (TEM) images were obtained with a JEOL 2100F fieldemission gun TEM.

An automated BET surface analyzer (Quantachrome Autosorb-3b) was usedfor measurements of sorbents' surface areas and pore volumes based on N₂adsorption-desorption. Typically, a ˜100 mg of sample was loaded into aquartz tube and pretreated at 130° C. under vacuum (˜5 mm Hg) in orderto remove sorbates before the measurement.

MAS NMR spectra were recorded on a Bruker Avance III 4.7 T spectrometerwith a standard MAS probe for 4 mm outer diameter rotors.

Example 1.4 Volumetric CO₂ Sorption Experiments (NIST)

CO₂ sorption measurements were carried out on computer-controlledcustom-built volumetric sorption equipment previously described indetail (J. Phys. Chem. C 111, 16131-16137 (2007)) with an estimatedreproducibility within 0.5% and isotherm data error bar of less than 2%compared to other commercial instruments. An amount of ˜79 mg of samplewas used for the experiments. Sample degassing, prior to the CO₂sorption experiment, was done at 130° C. under vacuum for 12 h.

Example 1.5 Gravimetric CO₂ Sorption Experiments

CO₂ sorption measurements were performed on a high pressure thermalgravimetric equipment (Model: TGA-HP50) from TA Instruments. An amountof ˜15 mg of sample was used for the experiments. Sample degassing,prior to CO₂ sorption experiment, was done at 130° C. under vacuum for12 h.

Example 1.6 Synthesis of S-Containing Porous Carbon (SPC)

Poly[(2-hydroxymethyl)thiophene] (PTh) (Sigma-Aldrich) was preparedusing FeCl3 Microporous Mesoporous Mater. 158, 318-323 (2012). In atypical synthesis, 2-thiophenemethanol (1.5 g, 13.1 mmol) in CH3CN (10mL) was slowly added under vigorous stirring to a slurry of FeCl₃ (14.5g, 89.4 mmol) in CH₃CN (50 mL). The mixture was stirred at roomtemperature for 24 h. The polymer (PTh) was separated by filtration overa sintered glass funnel, washed with distilled water (˜1 L) and thenwith acetone (˜200 mL). The polymer was dried at 100° C. for 12 h toafford (1.21 g, 96% yield) of the desired compound.

The PTh was activated by grinding PTh (500 mg) with KOH (1 g, 17.8 mmol)with a mortar and pestle and then heated under Ar at 600° C. in a tubefurnace for 1 h. The Ar flow rate was 500 sccm. After cooling, theactivated sample was thoroughly washed 3× with 1.2 M HCl (1 L) and thenwith distilled water until the filtrate was pH 7. The SPC sample wasdried in an oven at 100 C. to afford 240 mg of the black solid SPC. TheBET surface area and pore volume were 2500 m²/g and 1.01 cm³/g,respectively.

Example 1.7 Synthesis of N-Containing Porous Carbon (NPC)

Commercial polyacrylonitrile (PAN, 500 mg, average Mw 150,000,Sigma-Aldrich) powder and KOH (1500 mg, 26.8 mmol) were ground to ahomogeneous mixture in a mortar. The mixture was subsequently carbonizedby heating to 600° C. under Ar (500 sccm) in a tube furnace for 1 h. Thecarbonized material was washed 3 times with 1.2 M HCl (1 L) and thenwith distilled water until the filtrate was pH 7. Finally, the carbonsample was dried in an oven at 100° C. to afford 340 mg of the solidblack NPC.

To produce R-NPC, the activated material (270 mg) was further reduced by10% H₂ (H₂:Ar=50:450 sccm) at 600° C. for 1 h to provide 255 mg of thefinal material. The BET surface area and pore volume were 1450 m² g and1.43 cm³ g, respectively.

Example 1.8 Conversion of Excess Uptake to Absolute Uptake

Total uptake includes all gas molecules in the adsorbed state, which isthe sum of the experimentally measured excess uptake and the bulk gasmolecules within the pore volume (FIG. 6). For microporous materialswith negligible external surface area, the total uptake is often used asan approximation for absolute uptake and could be represented in thefollowing equation:

N _(total) ≈N _(abs) =Nex.+Vpρbulk(P,T)

In the above equation, Vp is the pore volume of porous material and ρbulk is the density of gas in the bulk phase at given pressure andtemperature. In the case of SPC, the pore volume was determined to be1.01 cm³ g by N₂ adsorption isotherm at 77 K (BET analysis). The CO₂density changes from 0.00180 to 0.06537 g/cm⁻³ in the pressure rangebetween 1 and 30 bar at 22° C. and 0.00164 to 0.05603 g/cm³ at 50 C.

Example 1.9 Determination of the Heat of CO₂ Sorption (Q)

The Clausius-Clapeyron equation (Adsorption 175, 133-137 (1995)) wasused to determine the heat of CO₂ sorption.

$\left( \frac{{\partial\ln}\; P}{\partial T} \right)_{\theta} = \frac{Q}{{RT}^{2}}$

In the above equation, θ is the fraction of the adsorbed sites at apressure P and temperature T, and R is the universal constant. Theequation can be further derived as the following expression fortransitions between a gas and a condense phase:

${{\ln \; P_{2}} - {\ln \; P_{1}}} = {\frac{Q}{R}\left( {\frac{1}{T_{1\;}} - \frac{1}{T_{2\;}}} \right)}$

Table 1 below compares the heat of CO₂ sorption to values in theliterature.

TABLE 1 Heat of CO₂ sorption determined in Example 1 versus literaturevalues. Q_(CO2) Comparison with (kJ mol⁻¹) reference SPC 57.8 59.0¹Activated carbon 28.4 28.9² Zeolite 5A 31.2 33.7³ ZIF-8 25.6 27.0⁴ Ref.¹ Carbon 50, 5543-5553 (2012). Ref. ² J. Natural Gas Chem. 15, 223-229(2006). Ref. ³ Handbook of Zeolite Science and Technology, MarcelDekker, Inc. New York (2003). Ref. ⁴ AIChE J. 59, 2195-2206 (2013).

Example 1.10 Evaluation of the 13C NMR Assignments

The three NMR spectra in FIG. 8D were obtained under identicalconditions: 12 kHz MAS, 2.5-μs 90° 13C pulse, 41-ms FID, 10-s relaxationdelay; 480 scans; and 50 Hz of line broadening applied to the FID.

Numerous MAS NMR investigations of CO₂ have reported a signal at 125±1ppm, regardless of the physical environment for the CO₂ (e.g., free gas,physisorbed on various materials, in a metal organic framework, in aclathrate, dissolved in a glass, etc.) Accordingly, attributing thesignal at 130.6 ppm to CO₂ physisorbed on the sorbent seems reasonable,although the reason for the additional deshielding may not be apparent.It is envisioned that this 5-ppm difference does not result from the useof different chemical shift references, as the various reports indicatethat either the signal from Si(CH3)₄ (TMS) serves as the chemical shiftreference (0 ppm) or that the signal from a solid such as adamantane orglycine (this work) relative to TMS at 0 ppm serves as the chemicalshift reference. Applicants note that the sorbent is somewhat conductivein that it has a noticeable effect on the tuning and matching of the 13Cand 1H channels of the NMR probe (relative to the tuning and matchingfor glycine). However, spinning is unaffected. Without being bound bytheory, it is envisioned that the conductive nature of the sorbentresults in the 5-ppm deshielding effect observed for physisorbed CO₂.

A chemical shift of 166.5 ppm is rational for poly(CO₂) in light ofvarious reports of bicarbonate and carbonate species giving signals from162 to 170 ppm relative to TMS or to [(CH₃)3Si]4Si, which is 3.5 ppmrelative to TMS at 0 ppm. The carbonyl chemical shift ofCH₃O—CO—O—CO—OCH₃ is extremely sensitive to its environment (thereported shift is 147.9 ppm as a neat liquid at 37° C. and 157 ppm inCDCl₃, both relative to TMS). Applicants are not aware of any reports ofchemical shift data for poly(CO₂) and are hereby reporting the firstsuch example of that chemical shift at 166.5 ppm when entrapped in thiscarbon matrix.

Example 2 CO₂ Absorption Capacities of Different Carbon Materials

In this example, the CO₂ uptake capacities of SPC, R-NPC, rice protein,ZIF-8 and Zeolite 5A were compared. The CO₂ uptake measurements wereconducted at 30° C. and 30 bar.

As shown in FIG. 13, the CO₂ uptake capacities of SPC and R-NPC weresignificantly higher than the CO₂ uptake capacities of ZIF-8, riceprotein, and Zeolite 5A.

Example 3 Asphalt-Derived Porous Carbons for CO₂ Capture

In this Example, Applicants report the preparation and CO₂ uptakecapacity of microporous carbon materials synthesized from asphalt.Carbonization of asphalt with potassium hydroxide (KOH) at hightemperatures (>873 K) yields asphalt-derived porous carbons (A-PC) withBrunauer-Emmett-Teller (BET) surface areas of up to 2800 mg and CO₂uptake capacities of up to 25 mmol/g at 30 bar and 298 K. Furthernitrogen doping of the A-PCs yields active N-doped A-PCs (also referredto as A-NPCs) containing up to 9.3 wt % nitrogen. The A-NPCs haveenhanced BET surface areas of up to 2900 m²g⁻¹ and CO₂ uptake capacitiesof up to 1.2 g at 30 bar and 298 K. Asphalt derived porous carbon withpre-treatment at 400° C. had measured BET surface areas of 4200 m²/g andCO₂ uptake capacities of up to 1.3 g at 30 bar and 298 K. To the best ofApplicants' knowledge, such results represent the highest reported CO₂uptake capacities among the family of activated porous carbon materials.Thus, the porous carbon materials derived from asphalt demonstrate therequired properties for capturing CO₂ at a well-head during theextraction of natural gas under high pressure.

Example 3.1 Synthesis and Characterization of Asphalt-Derived PorousCarbon Materials

Asphalt-derived porous carbons (A-PCs) were prepared by carbonization ofa molded mixture of asphalt and potassium hydroxide (KOH) at highertemperatures under inert atmosphere (Ar). The treatment of asphalt withKOH was conducted at various temperatures (200-800° C.) and asphalt/KOHweight ratios (varied from 1/1 to 1/5). In addition, the reactionconditions were adjusted and tuned by the CO₂ uptake performance of thefinal porous carbon materials.

In a more specific example, A-PC was synthesized at 700° C. at anasphalt:KOH weight ratio of 1:4. As shown in FIG. 14, the produced A-PChas a steep nitrogen uptake at low pressures (0-0.3 P/P_(o)), indicativeof the large amount of microporous structures with uniform distributionof pore sizes ˜1.3 nm (see FIG. 15 inset). The BET surface area (2779m²/g) and the pore volume (1.17 cm³/g) were calculated from the nitrogenisotherms (see Table 2). X-ray photoelectron spectroscopy (XPS) of theA-PC showed C 1s and O 1s signals with ˜10 wt % of oxygen content, whichare assigned to C—O and C═O functional groups (data not shown).

Scanning electron microscopy (SEM) images of the A-PCs show porousmaterials with uniform distribution of the micropores (FIG. 14A).Uniform distribution of the micropores are further indicated by thetransmission electron microscopy (TEM) images (FIG. 14B) that show porediameters of about 1.5 nm, which is very close to the number extractedfrom nitrogen absorption isotherms.

Treatment of A-PCs with NH3 at elevated temperatures resulted in N-dopedporous carbon materials (A-NPC) (FIG. 16A). The nitrogen content and thesurface area increased considerably after treatment of A-PCs with NH3 athigher temperatures, as shown in Tables 2 and 3. This leads to theformation of A-NPCs with a nitrogen concentration of up to 9.3 wt %.

TABLE 2 Properties and CO₂ uptake capacities of various porous carbons.Properties and CO₂ uptake capacities of various porous carbons. Pore CO₂uptake S_(BET) volume Density capacity at 30 bar Samples (m²/g)^(a)(cm³/g)^(a) (g/cm³) (g/g)^(b) A-PC 2779 1.17 2 0.96 A-NPC 2858 1.20 21.10 A-rNPC 2583 1.09 2 1.19 SPC 2500 1.01 2.21 0.74 NPC 1490 1.40 1.80.60 rNPC 1450 1.43 1.8 0.67 ^(a)Estimated from N₂ absorption isothermsat 77 K, where samples were dried at 200° C. for 20 h prior to themeasurements. ^(b)CO₂ uptake capacity at 23° C.

TABLE 3 Elemental composition and CO₂ uptake capacities of activatedporous carbons. Elemental composition and CO₂ uptake capacities ofactivated porous carbons. CO₂ uptake XPS capacity Pyridinic PyrrolicGraphitic at 30 bar Samples C % O % N % N % N % N % (g/g)^(a) A-NPC(500)91.1 6.1 2.7 29.7 63.3 7.0 1.02 A-NPC(600) 90.6 6.4 3.0 33.1 52.6 14.31.04 A-NPC(700) 91.1 4.2 4.7 53.2 41.4 5.4 1.06 A-NPC(800) 81.0 9.7 9.352.3 45.4 2.3 0.93 A-rNPC 88.0 7.5 4.5 55.1 40.3 4.6 1.19 ^(a)CO₂ uptakecapacity at 23° C.

The surface N-bonding configurations reveal three main nitrogenfunctional groups in the surface of the carbon framework. As shown inFIG. 14A, the N 1s spectra at variable doping temperatures deconvolutedinto three peaks with binding energies of about 399, 400.7±4, and about401.7. These binding energies are in the range of typical bindingenergies corresponding to pyridinic N, pyrollic N and graphitic N,respectively. The new peak at the binding energy of about 396 wasobserved at 800° C., which was assigned to the N—Si binding energy.Without being bound by theory, it is envisioned that, at high pyrolysistemperatures, NH₃-doping of silica from the quartz reaction tube startsto interfere with the doping process.

Further H₂ treatment of A-NPCs at 700° C. resulted in formation ofreduced A-NPCs (A-rNPC). The elemental composition and the surface areaof the A-rNPCs were investigated using XPS (see FIG. 14B and Table 3).The XPS spectrum of the produced A-rNPCs (FIG. 14B) is similar to theXPS spectrum of A-NPCs (FIG. 14A). A schematic representation of thesynthetic route for the production of A-rNPCs is shown in FIG. 16A.

Applicants also observed that, as reaction temperatures increased, therelative trend of the pyrrolic nitrogens in A-NPCs increased. However,the opposite was observed for pyridinic nitrogens. These resultsindicate that pyrolysis temperature during NH₃ treatment plays asignificant factor in determining the CO₂ uptake performance of A-NPCs.

Example 3.2 CO₂ Uptake Capacity of the Asphalt Derived Porous CarbonMaterials

The CO₂ uptake capacities of A-PC, A-NPC, and A-rNPC were compared tothe CO₂ uptake capacities of prior porous carbon materials, includingnitrogen containing nucleophilic porous carbons derived frompoly(acrylonitrile) (NPCs), sulfur containing porous carbons derivedfrom poly[(2-hydroxymethyl)thiophene (SPCs), commercial activatedcarbon, and asphalt (the NPCs and SPCs were described previously inPCT/US2014/044315 and Nat Commun., 2014 Jun 3, 5:3961, doi:10.1038/ncomms4961). The CO₂ uptake capacities were measured by avolumetric method at room temperature over the pressure range of 0-30bar. The results are shown in FIG. 17.

Applicants also observed that volumetric CO₂ uptake by A-PC, A-NPC andA-rNPC do not show any hysteresis (data not shown). Such observationssuggest that the asphalt-derived porous carbon materials uptake CO₂ in areversible manner. The CO₂ uptake capacities at a pressure of 30 bar aresummarized in Tables 2 and 3.

A-rNPC has the highest CO₂ uptake performance at 30 bar, although thehighest surface is obtained for A-NPC. As Applicants increased theN-doping temperature (from 500° to 800° C.), pyrollic nitrogen starts todecrease in intensity, which is linearly proportional to the CO₂ uptakeperformance of the A-NPCs (see Table 3). Thus, without being bound bytheory, Applicants envision that pyrrolic nitrogens play a moresignificant role in CO₂ uptake performance than the bulk nitrogencontent of the porous carbon material.

FIG. 18 shows the high and low pressure CO₂ uptake capacity of A-rNPC astemperature increases. As in other solid physisorbents such as activatedcarbons, zeolites and MOFs, the CO₂ uptake capacity decreases withincreasing temperature. However, when compared with commercial activatedcarbon and SPC, the decrease in CO₂ uptake at higher temperature islower. This suggests the higher and uniform microporosity of A-rNPCs, orthe efficacy of poly(CO₂) formation.

Another key property of the activated carbon materials is the CO₂/CH4selectivity. In order to evaluate the CO₂/CH₄ selectivity of A-PC, A-NPCand A-rNPCs, Applicants compared CH₄ uptake performances with SPC,activated carbon, and ZIF-8 sorbents over the 0-30 bar pressure range at23° C. FIG. 19 shows the comparison of the CO₂ and CH₄ sorptioncapacities of A-rNPC and SPC. A-rNPCs have higher CH₄ (8.6 mmol/g)uptake relative to SPC (7.7 mmol/g) at 30 bar, which is in agreementwith the higher surface area for A-rNPC (2583 m²/g) than the SPC (2500m²/g).

The molar ratios of sorbed CO₂ and CH₄ (nCO2/nCH4) were estimated as theratios of the amount of absorbed gases at 30 bar. The measured nCO₂/nCH₄for A-rNPC was found to be about 3.5. This value was compared to valuesfor SPC (2.6), activated carbon (1.5) and ZIF-8 (1.9).

In addition, the isosteric heat of absorption of CO₂ and CH₄ on thesurfaces of A-PC, A-NPC and A-rNPC were calculated using low pressureCO₂ sorption isotherms at 23° C. and 80° C. The measured value was foundto be about 27 kJ/mol.

Example 3.3 CO₂ Uptake Capacity of Asphalt Derived Porous Carbon withPre-Treatment

Similar to example 3.1, asphalt-derived porous carbons were prepared bycarbonization of a molded mixture of asphalt and potassium hydroxide(KOH) at higher temperatures under inert atmosphere (Ar). The treatmentof asphalt with KOH was conducted at various temperatures (200-800° C.)and asphalt/KOH weight ratios (varied from 1/1 to 1/5). An additionalpre-treatment step of heating the asphalt prior to mixing with KOH forcarbonization was done to remove volatile oils found within the asphaltsource (FIG. 31). In this specific example, untreated Gilsonite (uGil)was heated specifically at 400° C., then mixed with KOH, andsubsequently reacted at temperatures 600° C. and greater to tune the CO₂uptake performance of the final porous carbon materials. Table 4summarized the high surface area and even higher CO₂ uptake capacityachievable with pre-treatment and increasing reaction temperature.

FIG. 20 shows the gravimetric CO₂ uptake and CH₄ uptake of variousporous carbon samples made from Gilsonite and measured under highpressure. The molar ratios of sorbed CO₂ and CH₄ (nCO2/nCH4) wereestimated as the ratios of the amount of absorbed gases at 30 bar. Themeasured nCO₂/nCH₄ for uGil-800 and uGil-900 were found to beapproximately 8 (results not shown). This value can be compared tovalues for A-rNPC (3.5), SPC (2.6), activated carbon (1.5) and ZIF-8(1.9). Such CO₂ uptake capacities (i.e., up to 30 mmol/g) are thehighest reported CO₂ uptake capacities among the activated carbons. SuchCO₂ uptake capacities are also comparable to the highest CO₂ uptakecapacities of synthetic metal-organic frameworks (MOFs).

TABLE 4 Properties and CO₂ uptake performances of activated porouscarbons made from Untreated Gilsonite. CO₂ uptake Total pore capacityS_(BET) volume D_(pore) XPS at 30 bar^(d) Samples (m²/g)^(a) (cm³/g)^(b)(nm)^(c) C % O % mmol/g wt % uGil-600 2300 1.31 2.13 84.9 15.1 18.6 82uGil-700 3800 2.11 2.21 88.7 11.3 23.8 105 uGil-800 3900 2.22 2.25 91.58.5 25.7 113 uGil-900 4200 2.41 2.30 92.1 7.9 29.1 128 ^(a)Surface areaestimated from N₂ absorption isotherms at 77 K; samples dried at 240° C.for 20 h prior to the measurements. ^(b)Total (micro- and meso-) porevolume obtained at P/P₀ = 0.994. ^(c)Average pore diameter (D_(pore)).^(d)CO₂ uptake at 23° C.

Example 4 Asphalt-Derived Porous Carbons for CO₂ and H₂S Capture

This Example pertains to the further production and characterization ofA-NPCs, A-SPCs, A-rNPCs, and A-NSPCs. In addition, this Example pertainsto the use of the aforementioned carbon materials for the capture ofboth CO₂ and H₂S.

Example 4.1 Synthesis and Characterization of Asphalt-Derived PorousCarbon Materials

Asphalt carbon sources were ground with KOH in a mortar. The weightratio of KOH to the asphalt carbon source was from about 1:3 to about1:4. The homogeneous powder was heated at 500-800° C. under Aratmosphere for 1 hour. This was followed by filtration and washing with10 wt % HCl_((aq)) and copious amounts of DI water until the extractswere neutral. The filtered sample was then dried at 110° C. until aconstant weight was obtained. The above steps produced A-PC.

A-NPC was prepared by annealing the A-PC at 700° C. for 1 hour under anNH₃-containing atmosphere. A-rNPC was prepared by further reduction ofA-NPC with 10 wt % H₂ at 700° C. for 1 h. A-SPC was prepared by exposingthe A-PC to a sulfur source and annealing the sulfur impregnated A-PC at650° C. for 1 h. A-NSPC was prepared by annealing the produced A-SPC for1 hour under an NH₃-containing atmosphere to yield A-NSPC.

Next, the produced porous carbon materials were characterized and testedfor uptake of CO₂ and H₂S. The results are summarized in Table 5.

TABLE 5 The properties and gas uptake capacities of variousasphalt-derived porous carbon materials. Asphalt-Versatrol HTGilstonite, a naturally occurring asphalt from MI SWACO, was used as acontrol. The H₂S uptake capacities of the porous carbon materials weremeasured as a function of the amount of sulfur retained on the porouscarbon material. CO₂ Textural H₂S Uptake Properties Chemical CompositionUptake Capacity SBET (atomic %) Capacity at 30 bar Sample (m2/g) N C O S(g/g) (g/g) Asphalt* 0.6 — — — — — 0.05 A-PC 2,613 0.5 91.4 8.1 — 1.060.92 A-NPC 2,300 5.7 91.0 3.3 — 1.50 1.01 A-rNPC 2,200 3.6 92.7 3.7 —2.05 1.12 A-SPC 2,497 — 90.3 7.1 2.7 — 1.16 A-NSPC 2,510 1.6 86.7 11.00.7 — 1.32

In order to characterize the H₂S uptake capacities of the porous carbonmaterials, the porous carbon materials were first dried at 120° C. for 1hour under vacuum (0.05 Torr). Next, the porous carbon material wastreated with H₂S under an air flow for 1 hour. The amount of sulfurretained on the porous carbon material was measured by thermogravimetricanalysis (TGA).

After H₂S uptake and air oxidation to S, A-rNPC was furthercharacterized by TEM EDS elemental mapping. As shown in FIG. 21, sulfuris uniformly distributed within the pores of A-rNPCs. In addition, theTGA curve of the A-rNPCs after H₂S uptake and conversion to sulfur isshown in FIG. 21.

The H₂S uptake of A-rNPC was also measured under different conditions,including inert or oxidative conditions. The results are summarized inFIG. 23. The results show that A-rNPC can capture H₂S effectively in thepresence of O₂ from air. When CO₂ was present, A-rNPC also showed H₂Scapture behavior. The air conditions can mimic H₂S capture by porouscarbon materials during natural gas flow from a wellhead, injection of aslug of air to convert the sorbed H₂S to S, and the continuation of H₂Scapture from the natural gas source.

Without being bound by theory, it is envisioned that, as a result of thebasic functional groups on the surface of A-NPCs and A-rNPCs, and as aresult of the pH values of A-NPCs (pH=7.2) and A-rNPCs (pH=7.5), theporous carbon materials of the present disclosure can capture H2S by anacid-base reaction, where an amine group on the porous carbon abstractsa proton from H2S to yield the ammonium salts and hydrogen monosulfideanions according to the following scheme:

R₃N (where R is the carbon scaffold or a proton)+H₂S→R₃NH⁺ or R₂SH⁺+HS⁻

In this case, the equilibrium constant (k_(eq)) is ˜1000 based on thepKa values of the starting materials (H₂S) and products (ammoniumspecies). As a result of the reaction of HS ions with O₂ from airintroduced in the carbon support, the captured H₂S produces sulfurproducts such as S, SO₂ and H₂SO4. The catalytic oxidation of H₂S onA-NPC, A-rNPC and A-PC can proceed at room temperature by air oxidation.

Applicants also observed that nitrogen doping doubles the H₂S capturingcapacity of the porous carbon materials (FIGS. 22-23 and Table 5).Without being bound by theory, it is envisioned that the extent ofoxidation appears to be driven by the distribution of the catalyticcenters, such as nitrogen-containing basic functional groups.Additionally, Applicants observed that the oxidative capturing of H₂S byA-PCs can form sulfur-impregnated A-PCs (A-SPCs) upon heating at 650° C.(FIG. 16B).

The CO₂ uptake capacities of the porous carbon materials were alsoevaluated. As shown in FIG. 24, the CO₂ uptake capacities of A-NPCs andA-rNPCs were evaluated from 0 bar to 30 bar at 23° C. A-rNPC exhibitshigh CO₂ uptake capacity (1.12 g CO₂/g ArNPC) under a higher pressureenvironment, which is 5 times higher than Zeolite 5A, and 3 times higherthan ZIF-8 under the same conditions. Such CO₂ uptake capacities alsoexceed about 72 wt % of the CO₂ uptake capacities observed onnitrogen-containing porous carbon (NPC) that were reported inApplicants' pervious patent application (PCT/US2014/044315).

As shown in FIG. 25, the CO₂ uptake capacities of A-SPCs and A-NSPC werealso evaluated from 0 to 30 bar at 23° C. The A-NSPCs had been madeaccording to the scheme illustrated in FIG. 16B, where it alreadycompleted its life as an H₂S capture material, with air oxidation to asulfur-rich carbon, then thermalization to form A-SPC, or furtherexposure to NH3 to form the A-NSPC. These latter two materials are shownin FIG. 25 to be used for reversible capture of CO₂. This underscoresthe utility life of these porous carbon materials—first for irreversiblecapture of H₂S as sulfur in over 200 wt % uptake, and then conversion toA-SPC or A-NSPC for reversible capture of CO₂ in over 100 wt % uptake.A-SPCs exhibited high CO₂ uptake capacities (in excess of 1.10 g CO₂/gA-SPCs) under pressure environment, which is 5 times higher in uptake ofCO₂ than Zeolite 5A, and 3 times higher in uptake of CO₂ than ZIF-8under the same conditions. Such CO₂ uptake capacities also exceed about89 wt % of the CO₂ uptake capacities observed on sulfur-containingporous carbons (SPC) reported in Applicants' pervious patent application(PCT/US2014/044315).

Example 5 Synthesis of Porous Carbon Materials

In this Example, Applicants provide exemplary schemes for the synthesisof porous carbon materials.

Example 5.1 Scheme A

Carbon sources suitable for use in the present disclosure are mixed witha vulcanization agent and heated to 180° C. for 12 hours in accordancewith the following scheme:

Carbon source+vulcanization agent→porous carbon material

The weight ratio of the vulcanization agent to the carbon source variedfrom 5 wt % to 200 wt % relative to the carbon source. The vulcanizedcarbon source obtained was then treated with KOH, as described inExample 2.1.

Example 5.2 Scheme B

Carbon sources suitable for use in the present disclosure are mixed witha vulcanization agent and elemental sulfur and heated to about 180° C.for 12 h in accordance with the following scheme:

Carbon source+vulcanization agent+elemental sulfur→porous carbonmaterial

The weight ratio of the vulcanization agent to the carbon source variedfrom 5 wt % to 200 wt % relative to the carbon source. The obtainedvulcanized carbon source was then treated with KOH as described inExample 2.1.

Example 5.3 Scheme C

Carbon sources suitable for use in the present disclosure are mixed witha vulcanization agent, elemental sulfur, and KOH in accordance with thefollowing scheme:

Carbon source+vulcanization agent+KOH→porous carbon material

The homogeneous powder is then heated at 600˜800° C. under Ar atmospherefor 1 hour. This is followed by filtration with 10 wt % HCl_((aq)) andcopious amounts of DI water. The weight ratio of the vulcanization agentwas chosen from 5 wt % to 200 wt % additive relative to the carbonsource. The weight ratio of KOH to the carbon source varied from 1 to 3.

Example 5.4 Scheme D

Carbon sources suitable for use in the present disclosure are mixed witha vulcanization agent, elemental sulfur, and KOH in accordance with thefollowing scheme:

Carbon source+vulcanization agent+elemental sulfur+KOH→porous carbonmaterial

The homogeneous powder is then heated at 600-800° C. under Ar atmospherefor 1 h. This is followed by filtration with 10 wt % HCl_((aq)) andcopious amounts of DI water. The weight ratio of the elemental sulfur tothe carbon source varied from 0.2 to 1. The weight ratio of thevulcanization agent to the carbon source varied from 5 wt % to 200 wt %relative to the carbon source. The weight ratio of KOH to the carbonsource was chosen from 1 to 3.

In summary, Applicants have demonstrated in Examples 1-3 the firstsuccessful synthesis of microporous active carbons with uniformdistribution of pores sizes from asphalt. Applicants subsequentlyactivated the asphalt derived porous carbon materials with nitrogenfunctional groups. By changing the reaction conditions, the porouscarbon materials can possess variable surface areas and nitrogencontents. The CO₂ and H₂S uptake capacities of the asphalt-derivedporous carbon materials are higher than other porous carbon materials.Additionally, many of the porous carbon materials derived from asphaltexhibit greater CO₂:CH₄ selectivity than other porous carbon materials.Furthermore, as summarized in Table 6, the carbon sources of the presentdisclosure are much more affordable than the carbon sources utilized tomake other porous carbon materials.

TABLE 6 A comparison of the costs of various carbon sources. CarbonSource Cost 2-thiophene methanol (to make traditional SPC) $150/100 g(Aldrich) Polyacrylonitrile (to make traditional NPC) $180/100 g(Aldrich) Whey Protein $11/lb Rice Protein $9/lb Coal $70-150/tonAsphalt $70-750/ton

Example 5.5 Scheme E

Carbon sources suitable for use in the present disclosure are initiallyheated at 400° C. This allows for the removal of volatile oils that arepresent in the carbon source (FIG. 31). This is termed the pre-treatmentstep in the synthesis of porous carbon. The pre-treated carbon source isthoroughly mixed with KOH in accordance with the following scheme:

The homogeneous powder is then heated at 600˜900° C. under Ar atmospherefor 1 hour. This is followed by filtration with 10 wt % HCl_((aq)) andcopious amounts of DI water. The weight ratio of KOH to the carbonsource was chosen from 1 to 4.

Example 6 Synthesis of Porous Carbon Materials from Biomass

In some embodiments, additional low cost raw materials may be used toprepare the porous carbon materials of the invention. For example, theporous carbon materials of the present disclosure may be derived from atleast one of biochars hydrochars, charcoals, wood waste, activatedcarbon, and combinations thereof. The embodiments (e.g., B-PC and B-NPCmaterials) may be produced in a one-step synthesis method which issimple, inexpensive and easy to scale up. In some embodiments, theporous carbon materials of the present disclosure can be easily preparedfrom low-cost or negative-cost biomass by pyrolysis in the presence oflittle or no oxygen at temperatures of 200-900° C. In some embodiments,the biomass includes agricultural crops, crops residues, plantations,grass, wood, animal litter, dairy manure, solid waste, and combinationsthereof. In some embodiments, the biomass utilized to make the porouscarbon materials of the present disclosure is abundant (in fact, peoplehave to pay money to get rid of biomass waste).

In some embodiments, hydrochar, charcoal and other carbon-containingmaterials can be utilized for the manufacture of the porous carbonmaterials of the present disclosure. Hydrochar is similar to biochar andit is produced by hydrothermal carbonization of biomass under pressurein the presence of water at high temperature (typically 150-300° C.).Charcoal is also similar to biochar, although it is often used for fueland energy generation.

Therefore, the porous carbon materials of the present disclosure can beprepared by simple and economical synthesis procedures from abundant andinexpensive precursors to make solids for the capture of CO₂ and H₂S.Moreover, the porous carbon materials of the present disclosure areenvironmentally attractive. For example, trees and plants, when alive,capture CO₂ and convert it to oxygen and carbon. Here, Applicants showthat trees and plants, when dead, can continue to trap CO₂. And sincethe porous carbon materials of the present disclosure (e.g., B-PC andB-NPC) are reusable many times, the CO₂ capture efficacy of a “dead”tree or plant can exceed that of the living tree or plant. Moreover, theporous carbon materials of the present disclosure (e.g., B-PC and B-NPC)can be manufactured on industrial scales.

In some embodiments, the porous carbons of the present disclosure can bemade by the following steps:

Carbon sources can include, without limitation, biochar (e.g., biocharfrom mesquite, applewood, corncobs and corn stover, straw from wheat,bagasse, lignin, urban tree cutting, bull, dairy, hazelnut, oak, pine,food, paper, cool terra, waste, etc); charcoal (e.g., charcoal fromwood, saw dust, other wood waste, etc); activated carbon from varioussources, and combinations thereof. Melamine resin can also be replacedby melamine. Sulfur-containing organics, such as those used incrosslinking rubber, can be used to make the sulfur analogs, B-SPC,which can likewise capture CO₂ and H₂S.

Synthesis of porous carbon materials, B-PC and B-NPC. (a) Synthesis ofbiochar derived porous carbon (B-PC). The carbon sources listed abovewere mixed with KOH in a mortar. The weight ratio of KOH to carbonsources was chosen from 2 to 6 and the carbonization temperature waschosen in the range of 600° C. to 900° C. The product was filtered andwashed with DI water until the effluent was neutral, followed by dryingat 110° C. in the oven for 12 h. (b) Synthesis of biochar derivednitrogen-containing porous carbon (B-NPC). The carbon sources andmelamine resin were mixed with KOH in a mortar. The ratio of KOH tocarbon sources was chosen from 2 to 6, the ratio of melamine to carbonsource was chosen from 0 to 1, and the carbonization temperature waschosen from 600° C. to 900° C. The product was purified and dried in thesame way as B-PC.

FIG. 26. (a) SEM image of B-NPC and, (b) TEM image of B-NPC, (c) BETisotherm curve of B-NPC, indicating B-NPC is microporous material withsurface area of 2988 m²/g, (d) DFT size distribution of B-NPC and thepore size is from 0.5-5 nm.

TABLE 7 Physical and chemical properties and CO₂ uptake and H₂S uptakeof biochar derived porous carbon. The weight ratio of KOH to biochar is5 and the carbonization temperature is 800° C. (Biochar was Mesquitebiochar pyrolyzed at 450° C. Textural Chemical properties compositionCO₂ S_(BET) (atomic %) H₂S uptake uptake capacity Sample (m²/g) N C OCapacity (g/g) at 30 bar (g/g) Biochar 9.9 1.6 83.5 14.9 — 0.14 B-PC2,988 — 93.0 7.0 — 1.13 B-NPC 2,908 0.6 91.4 9.0 0.41 1.14

TABLE 8 Physical properties and CO₂ uptake of different biochar derivedporous carbons. (Biochar was Mesquite biochar pyrolyzed at 450° C.Weight of reactants (g) Textural CO₂ Melamine properties uptake capacitySample Biochar resin KOH S_(BET) (m²/g) Yield (wt %) at 30 bar (g/g)B-PC (1) 0.50 0 2.50 2988 40 1.13 B-PC (2) 0.50 0 3.00 2755 28 1.15B-NPC (1) 0.50 0.25 2.50 2908 45 1.14 B-NPC (2) 0.50 0.25 3.00 3133 411.20 B-NPC (3) 0.50 0.25 3.50 2273 20 1.05 C-NPC 0.50* 0.25 2.50 3469 281.26 *Activated charcoal from Sigma Aldrich (CAS C3345, Lot # 051M0151Mxxxx) is used as precursor.

FIG. 27. CO₂ uptake performances of different sorbents, B-NPC and C-NPC(charcoal derived N-containing porous carbon) at 25° C. B-NPC derivedfrom mesquite exhibits high CO₂ capacity (1.14 g/g) at 30 bar, which is5 times higher than Zeolite 5A, 3 times higher than ZIF-8 under the sameconditions. C-NPC derived from charcoal exhibits high CO₂ capacity (1.26g/g) at 30 bar, which is 5.7 times higher than Zeolite 5A, 3.4 timeshigher than ZIF-8 at the same conditions. Both of them show much betterCO₂ uptake amount than their own precursor. B-PC shows similar or betterCO₂ uptake amount compared with asphalt derived porous carbon or polymer(polyacrylonitrile or poly[(2-hydroxymethyl)thiophene]) derived porouscarbon (NPC or SPC) as reported in prior applications.

FIG. 28. CO₂ uptake performances of different B-PC prepared by differentbases. KOH treated B-PC exhibits 1.13 g/g CO₂ uptake at 30 bar, which isbetter than NaOH or LiOH treated B-PC, which is 0.98 g/g or 0.55 g/g,respectively.

FIG. 29. CO₂ uptake performances of different B-NPC prepared fromdifferent precursors using KOH as base. The CO₂ uptake amounts of B-PCfrom mesquite (450° C.), applewood (450° C.), CoolTerra™, mesquite (700°C.), and waste (450° C.) are 1.14 g/g, 1.07 g/g, 0.87 g/g, 0.41 g/g, and0.39 g/g, respectively.

FIG. 30. Thermogravimetric analysis (TGA) curves of B-NPC and C-NPCafter H2S capture. The weight loss of sulfur rich B-NPC and C-NPC is 41%and 6.8%, respectively. By calculation, the H₂S capture capacity ofB-NPC and C-NPC is 0.74 g/g and 0.07 g/g.

Without further elaboration, it is believed that one skilled in the artcan, using the description herein, utilize the present disclosure to itsfullest extent. The embodiments described herein are to be construed asillustrative and not as constraining the remainder of the disclosure inany way whatsoever. Although the embodiments have been shown anddescribed, many variations and modifications thereof can be made by oneskilled in the art without departing from the spirit and teachings ofthe invention. Accordingly, the scope of protection is not limited bythe description set out above, but is only limited by the claims,including all equivalents of the subject matter of the claims. Thedisclosures of all patents, patent applications and publications citedherein are hereby incorporated herein by reference, to the extent thatthey provide procedural or other details consistent with andsupplementary to those set forth herein.

What is claimed:
 1. A material for use in CO₂ capture in high pressureenvironments, the material comprising, a porous carbon materialcontaining a plurality of pores for use in a high pressure environmenthaving a total pressure in the environment between about 2.5 to about100 bar, to selectively capture CO₂ over hydrocarbons in theenvironment, wherein a majority of the plurality of pores in the porouscarbon material have a diameter of about 3 nm or less, wherein thesurface area of the porous carbon material is between about 2,500 m²/gand about 4,500 m²/g, wherein the density of the porous carbon materialis between about 0.3 g/cm³ to about 4 g/cm³, and wherein the CO₂absolute sorption capacity of the porous carbon material is betweenabout 50 wt % and about 200 wt %.
 2. The material of claim 1, whereinthe porous carbon material is an asphalt-derived porous carbon.
 3. Thematerial of claim 1, wherein the porous carbon material is produced froma high fixed carbon content precursor selected from a group consistingof biochar, hydrochar, coal, lignite, biomass, organic substancescontaining heteroatoms such as nitrogen or sulfur, and combinationsthereof; wherein the precursor is heated at temperatures greater than600° C.; and wherein CO₂ selectivity and CO₂ capacity of the porouscarbon material is enhanced by functionalization of the porous carbonmaterial surface during such heating.
 4. The material of claim 1,wherein the porous carbon material is produced from a high fixed carboncontent precursor selected from a group consisting of biochar,hydrochar, coal, lignite, biomass, organic substances containingheteroatoms such as nitrogen or sulfur, and combinations thereof; andwherein the precursor is activated at a temperature between about 650°C. and about 1000° C. and in the presence of an amount of activatingagent, to create and maintain micropores within the porous carbonmaterial.
 5. The material of claim 1, wherein, after capture, the CO₂forms poly(CO₂) or a matrix of CO₂ within the porous carbon material. 6.The material of claim 1, wherein the porous carbon material has a CO₂uptake of between about 0.92 g/g to about 1.50 g/g, at a CO₂ pressure orpartial pressure of about 30 bar.
 7. The material of claim 1, whereinthe porous carbon material selectively captures CO₂ over CH₄, such thatthe molecular ratio between CO₂/CH₄ is between about 2 and about
 10. 8.A method of capturing CO₂, the method comprising: associating a CO₂containing environment with a high surface area, porous carbon materialthat includes a plurality of moieties; wherein the environment isselected from the group consisting of industrial gas streams, naturalgas streams, natural gas wells, industrial gas wells, oil and gasfields, and combinations thereof, wherein the environment is pressurizedto a total pressure between about 2.5 bar to about 100 bar; wherein themajority of the pores in the porous carbon material having a diameter ofabout 3 nm or less, wherein the density of the porous carbon material isbetween about 0.3 g/cm³ to about 4 g/cm³, and wherein the CO₂ sorptionabsolute capacity of the porous carbon material is between about 50 wt %and about 200 wt %; and selectively capturing CO₂ over hydrocarbonspecies in the environment with the porous carbon material.
 9. Themethod of claim 8, wherein the selectively capturing comprises: sorptionof CO₂ to the porous carbon material between atmospheric pressure and100 bar total or partial pressure, and selectively capturing CO₂ fromthe hydrocarbons in the environment; wherein the sorption of the CO₂occurs without heating the porous carbon material or the environment;and wherein, after sorption, the CO₂ forms poly(CO₂) or a matrix of CO₂within the porous carbon material.
 10. The method of claim 8, furthercomprising releasing the CO₂ from the porous carbon material after ithas been captured; wherein the release of the CO₂ occurs at totalpressures ranging from about 0.01 bar to about atmospheric pressure; andwherein the release of the CO₂ occurs without heating the porous carbonmaterial or the environment.
 11. The method of claim 8, where in therelease of the CO₂ is enhanced by the addition of heat to the porouscarbon material or to the environment.
 12. A method of capturing CO₂,the method comprising: associating a CO₂ containing environment with ahigh surface area, porous carbon material that comprises a plurality ofmoieties; selectively capturing CO₂ over hydrocarbon species with theporous carbon material; releasing the CO₂ from the porous carbonmaterial after it has been captured; and reusing the porous carbonmaterial for CO₂ capture subsequent to the releasing step, wherein theenvironment has a total or partial pressure between about 2.5 to about100 bar, and wherein the majority of the pores in the porous carbonmaterial have a diameter of about 3 nm or less.
 13. The method of claim12, wherein the environment is selected from the group consisting ofindustrial gas streams, natural gas streams, natural gas wells,industrial gas wells, oil and gas fields, and combinations thereof. 14.The method of claim 12, wherein, after selective capture, the CO₂ formspoly(CO₂) or a matrix of CO₂ within the porous carbon material.
 15. Themethod of claim 12, wherein the porous carbon material has a CO₂ uptakeof between about 0.92 g/g to about 1.50 g/g, at a CO₂ partial pressureof about 30 bar.
 16. The method of claim 12, wherein the porous carbonmaterial selectively captures CO₂ over CH₄, such that the molecularratio between CO₂ and CH₄ is between about 2 and about 10.